diff --git a/IntegrationTests/AppEventsTest.js b/IntegrationTests/AppEventsTest.js
index a109f42e4c35c6..4bc0b0649c16fa 100644
--- a/IntegrationTests/AppEventsTest.js
+++ b/IntegrationTests/AppEventsTest.js
@@ -36,7 +36,7 @@ class AppEventsTest extends React.Component<{}, State> {
     this.setState({sent: event});
   }
 
-  receiveEvent = (event: any) => {
+  receiveEvent: (event: any) => void = (event: any) => {
     if (deepDiffer(event.data, TEST_PAYLOAD)) {
       throw new Error('Received wrong event: ' + JSON.stringify(event));
     }
@@ -46,7 +46,7 @@ class AppEventsTest extends React.Component<{}, State> {
     });
   };
 
-  render() {
+  render(): React.Node {
     return (
       <View style={styles.container}>
         <Text>{JSON.stringify(this.state, null, '  ')}</Text>
diff --git a/IntegrationTests/AsyncStorageTest.js b/IntegrationTests/AsyncStorageTest.js
index d22a611064cf53..5df923c7f670ea 100644
--- a/IntegrationTests/AsyncStorageTest.js
+++ b/IntegrationTests/AsyncStorageTest.js
@@ -172,7 +172,7 @@ function testOptimizedMultiGet() {
 }
 
 class AsyncStorageTest extends React.Component<{}, $FlowFixMeState> {
-  state = {
+  state: any | $TEMPORARY$object<{|done: boolean, messages: string|}> = {
     messages: 'Initializing...',
     done: false,
   };
@@ -189,7 +189,7 @@ class AsyncStorageTest extends React.Component<{}, $FlowFixMeState> {
     AsyncStorage.clear(testSetAndGet);
   }
 
-  render() {
+  render(): React.Node {
     return (
       <View style={styles.container}>
         <Text>
diff --git a/IntegrationTests/ImageCachePolicyTest.js b/IntegrationTests/ImageCachePolicyTest.js
index 0dae9812cf6e24..d25e6c2b86ede3 100644
--- a/IntegrationTests/ImageCachePolicyTest.js
+++ b/IntegrationTests/ImageCachePolicyTest.js
@@ -36,9 +36,9 @@ type State = {
 };
 
 class ImageCachePolicyTest extends React.Component<Props, $FlowFixMeState> {
-  state = {};
+  state: $FlowFixMe | $TEMPORARY$object<{||}> = {};
 
-  shouldComponentUpdate(nextProps: Props, nextState: State) {
+  shouldComponentUpdate(nextProps: Props, nextState: State): boolean {
     const results: Array<?boolean> = TESTS.map(x => nextState[x]);
 
     if (!results.includes(undefined)) {
@@ -56,7 +56,7 @@ class ImageCachePolicyTest extends React.Component<Props, $FlowFixMeState> {
     this.setState({[name]: pass});
   }
 
-  render() {
+  render(): React.Node {
     return (
       <View style={styles.container}>
         <Text>Hello</Text>
diff --git a/IntegrationTests/ImageSnapshotTest.js b/IntegrationTests/ImageSnapshotTest.js
index c4ffaae51c2ec4..495423ae006340 100644
--- a/IntegrationTests/ImageSnapshotTest.js
+++ b/IntegrationTests/ImageSnapshotTest.js
@@ -22,11 +22,11 @@ class ImageSnapshotTest extends React.Component<{}> {
     }
   }
 
-  done = (success: boolean) => {
+  done: (success: boolean) => void = (success: boolean) => {
     TestModule.markTestPassed(success);
   };
 
-  render() {
+  render(): React.Node {
     return (
       <Image
         source={require('./blue_square.png')}
diff --git a/IntegrationTests/IntegrationTestHarnessTest.js b/IntegrationTests/IntegrationTestHarnessTest.js
index ea5e4f3a49b47e..148462286d6228 100644
--- a/IntegrationTests/IntegrationTestHarnessTest.js
+++ b/IntegrationTests/IntegrationTestHarnessTest.js
@@ -10,9 +10,10 @@
 
 'use strict';
 
-const requestAnimationFrame = require('fbjs/lib/requestAnimationFrame');
 const React = require('react');
 const ReactNative = require('react-native');
+
+const requestAnimationFrame = require('fbjs/lib/requestAnimationFrame');
 const {Text, View, StyleSheet} = ReactNative;
 const {TestModule} = ReactNative.NativeModules;
 
@@ -26,7 +27,7 @@ type State = {|
 |};
 
 class IntegrationTestHarnessTest extends React.Component<Props, State> {
-  state = {
+  state: State = {
     done: false,
   };
 
@@ -38,7 +39,7 @@ class IntegrationTestHarnessTest extends React.Component<Props, State> {
     }
   }
 
-  runTest = () => {
+  runTest: () => void = () => {
     if (this.props.shouldThrow) {
       throw new Error('Throwing error because shouldThrow');
     }
@@ -52,7 +53,7 @@ class IntegrationTestHarnessTest extends React.Component<Props, State> {
     });
   };
 
-  render() {
+  render(): React.Node {
     return (
       <View style={styles.container}>
         <Text>
diff --git a/IntegrationTests/LayoutEventsTest.js b/IntegrationTests/LayoutEventsTest.js
index 7be877f962456b..42def2c419b980 100644
--- a/IntegrationTests/LayoutEventsTest.js
+++ b/IntegrationTests/LayoutEventsTest.js
@@ -58,7 +58,7 @@ class LayoutEventsTest extends React.Component<Props, State> {
     this.setState({viewStyle: {margin: 60}});
   }
 
-  addWrapText = () => {
+  addWrapText: () => void = () => {
     debug('addWrapText invoked');
     this.setState(
       {extraText: '  And a bunch more text to wrap around a few lines.'},
@@ -66,14 +66,14 @@ class LayoutEventsTest extends React.Component<Props, State> {
     );
   };
 
-  changeContainer = () => {
+  changeContainer: () => void = () => {
     debug('changeContainer invoked');
     this.setState({containerStyle: {width: 280}}, () =>
       this.checkLayout(TestModule.markTestCompleted),
     );
   };
 
-  checkLayout = (next?: ?() => void) => {
+  checkLayout: (next?: ?() => void) => void = (next?: ?() => void) => {
     const view = this._view;
     const txt = this._txt;
     const img = this._img;
@@ -117,22 +117,22 @@ class LayoutEventsTest extends React.Component<Props, State> {
     }
   }
 
-  onViewLayout = (e: LayoutEvent) => {
+  onViewLayout: (e: LayoutEvent) => void = (e: LayoutEvent) => {
     debug('received view layout event\n', e.nativeEvent);
     this.setState({viewLayout: e.nativeEvent.layout}, this.checkLayout);
   };
 
-  onTextLayout = (e: LayoutEvent) => {
+  onTextLayout: (e: LayoutEvent) => void = (e: LayoutEvent) => {
     debug('received text layout event\n', e.nativeEvent);
     this.setState({textLayout: e.nativeEvent.layout}, this.checkLayout);
   };
 
-  onImageLayout = (e: LayoutEvent) => {
+  onImageLayout: (e: LayoutEvent) => void = (e: LayoutEvent) => {
     debug('received image layout event\n', e.nativeEvent);
     this.setState({imageLayout: e.nativeEvent.layout}, this.checkLayout);
   };
 
-  render() {
+  render(): React.Node {
     const viewStyle = [styles.view, this.state.viewStyle];
     const textLayout = this.state.textLayout || {width: '?', height: '?'};
     const imageLayout = this.state.imageLayout || {x: '?', y: '?'};
diff --git a/IntegrationTests/PromiseTest.js b/IntegrationTests/PromiseTest.js
index c36d3beb017b69..b35c971fc34816 100644
--- a/IntegrationTests/PromiseTest.js
+++ b/IntegrationTests/PromiseTest.js
@@ -16,10 +16,10 @@ const {View} = ReactNative;
 const {TestModule} = ReactNative.NativeModules;
 
 class PromiseTest extends React.Component<{}> {
-  shouldResolve = false;
-  shouldReject = false;
-  shouldSucceedAsync = false;
-  shouldThrowAsync = false;
+  shouldResolve: boolean = false;
+  shouldReject: boolean = false;
+  shouldSucceedAsync: boolean = false;
+  shouldThrowAsync: boolean = false;
 
   componentDidMount() {
     Promise.all([
@@ -37,19 +37,19 @@ class PromiseTest extends React.Component<{}> {
     );
   }
 
-  testShouldResolve = () => {
+  testShouldResolve: () => any = () => {
     return TestModule.shouldResolve()
       .then(() => (this.shouldResolve = true))
       .catch(() => (this.shouldResolve = false));
   };
 
-  testShouldReject = () => {
+  testShouldReject: () => any = () => {
     return TestModule.shouldReject()
       .then(() => (this.shouldReject = false))
       .catch(() => (this.shouldReject = true));
   };
 
-  testShouldSucceedAsync = async (): Promise<any> => {
+  testShouldSucceedAsync: () => Promise<any> = async (): Promise<any> => {
     try {
       await TestModule.shouldResolve();
       this.shouldSucceedAsync = true;
@@ -58,7 +58,7 @@ class PromiseTest extends React.Component<{}> {
     }
   };
 
-  testShouldThrowAsync = async (): Promise<any> => {
+  testShouldThrowAsync: () => Promise<any> = async (): Promise<any> => {
     try {
       await TestModule.shouldReject();
       this.shouldThrowAsync = false;
diff --git a/IntegrationTests/ReactContentSizeUpdateTest.js b/IntegrationTests/ReactContentSizeUpdateTest.js
index ad87bb6ed42f08..47373d6f2a8978 100644
--- a/IntegrationTests/ReactContentSizeUpdateTest.js
+++ b/IntegrationTests/ReactContentSizeUpdateTest.js
@@ -10,9 +10,9 @@
 
 'use strict';
 
+const RCTNativeAppEventEmitter = require('react-native/Libraries/EventEmitter/RCTNativeAppEventEmitter');
 const React = require('react');
 const ReactNative = require('react-native');
-const RCTNativeAppEventEmitter = require('react-native/Libraries/EventEmitter/RCTNativeAppEventEmitter');
 
 const {View} = ReactNative;
 
@@ -35,7 +35,7 @@ class ReactContentSizeUpdateTest extends React.Component<Props, State> {
   _timeoutID: ?TimeoutID = null;
   _subscription: ?EmitterSubscription = null;
 
-  state = {
+  state: State = {
     height: reactViewHeight,
     width: reactViewWidth,
   };
@@ -70,7 +70,9 @@ class ReactContentSizeUpdateTest extends React.Component<Props, State> {
     });
   }
 
-  rootViewDidChangeIntrinsicSize = (intrinsicSize: State) => {
+  rootViewDidChangeIntrinsicSize: (intrinsicSize: State) => void = (
+    intrinsicSize: State,
+  ) => {
     if (
       intrinsicSize.height === newReactViewHeight &&
       intrinsicSize.width === newReactViewWidth
@@ -79,7 +81,7 @@ class ReactContentSizeUpdateTest extends React.Component<Props, State> {
     }
   };
 
-  render() {
+  render(): React.Node {
     return (
       <View style={{height: this.state.height, width: this.state.width}} />
     );
diff --git a/IntegrationTests/SimpleSnapshotTest.js b/IntegrationTests/SimpleSnapshotTest.js
index 6ebf24fd25ac3a..90cb3f1e17c475 100644
--- a/IntegrationTests/SimpleSnapshotTest.js
+++ b/IntegrationTests/SimpleSnapshotTest.js
@@ -12,6 +12,7 @@
 
 const React = require('react');
 const ReactNative = require('react-native');
+
 const requestAnimationFrame = require('fbjs/lib/requestAnimationFrame');
 
 const {StyleSheet, View} = ReactNative;
@@ -25,11 +26,11 @@ class SimpleSnapshotTest extends React.Component<{}> {
     requestAnimationFrame(() => TestModule.verifySnapshot(this.done));
   }
 
-  done = (success: boolean) => {
+  done: (success: boolean) => void = (success: boolean) => {
     TestModule.markTestPassed(success);
   };
 
-  render() {
+  render(): React.Node {
     return (
       <View style={styles.container}>
         <View style={styles.box1} />
diff --git a/IntegrationTests/SizeFlexibilityUpdateTest.js b/IntegrationTests/SizeFlexibilityUpdateTest.js
index 2da24f0b920f9a..419083c57a319a 100644
--- a/IntegrationTests/SizeFlexibilityUpdateTest.js
+++ b/IntegrationTests/SizeFlexibilityUpdateTest.js
@@ -10,9 +10,9 @@
 
 'use strict';
 
+const RCTNativeAppEventEmitter = require('react-native/Libraries/EventEmitter/RCTNativeAppEventEmitter');
 const React = require('react');
 const ReactNative = require('react-native');
-const RCTNativeAppEventEmitter = require('react-native/Libraries/EventEmitter/RCTNativeAppEventEmitter');
 const {View} = ReactNative;
 
 const {TestModule} = ReactNative.NativeModules;
@@ -46,15 +46,15 @@ class SizeFlexibilityUpdateTest extends React.Component<Props> {
     }
   }
 
-  markPassed = () => {
+  markPassed: () => void = () => {
     TestModule.markTestPassed(true);
     finalState = true;
   };
 
-  rootViewDidChangeIntrinsicSize = (intrinsicSize: {
-    width: number,
+  rootViewDidChangeIntrinsicSize: (intrinsicSize: {
     height: number,
-  }) => {
+    width: number,
+  }) => void = (intrinsicSize: {width: number, height: number}) => {
     if (finalState) {
       // If a test reaches its final state, it is not expected to do anything more
       TestModule.markTestPassed(false);
@@ -99,7 +99,7 @@ class SizeFlexibilityUpdateTest extends React.Component<Props> {
     }
   };
 
-  render() {
+  render(): React.Node {
     return <View style={{height: reactViewHeight, width: reactViewWidth}} />;
   }
 }
diff --git a/IntegrationTests/TimersTest.js b/IntegrationTests/TimersTest.js
index c7eefb915333c3..8550c6f00eec6b 100644
--- a/IntegrationTests/TimersTest.js
+++ b/IntegrationTests/TimersTest.js
@@ -33,7 +33,7 @@ class TimersTest extends React.Component<Props, State> {
   _immediateIDs: Set<ImmediateID> = new Set();
   _animationFrameIDs: Set<AnimationFrameID> = new Set();
 
-  state = {
+  state: State = {
     count: 0,
     done: false,
   };
@@ -228,7 +228,7 @@ class TimersTest extends React.Component<Props, State> {
     }
   }
 
-  render() {
+  render(): React.Node {
     return (
       <View style={styles.container}>
         <Text>
diff --git a/IntegrationTests/WebSocketTest.js b/IntegrationTests/WebSocketTest.js
index 0d2cd5e0b4d9e7..fcc2d74cb8d35c 100644
--- a/IntegrationTests/WebSocketTest.js
+++ b/IntegrationTests/WebSocketTest.js
@@ -113,7 +113,7 @@ class WebSocketTest extends React.Component<{}, State> {
     this.testConnect();
   }
 
-  testConnect = () => {
+  testConnect: () => void = () => {
     this._connect();
     this._waitFor(this._socketIsConnected, 5, connectSucceeded => {
       if (!connectSucceeded) {
@@ -124,7 +124,7 @@ class WebSocketTest extends React.Component<{}, State> {
     });
   };
 
-  testSendAndReceive = () => {
+  testSendAndReceive: () => void = () => {
     this._sendTestMessage();
     this._waitFor(this._receivedTestExpectedResponse, 5, messageReceived => {
       if (!messageReceived) {
@@ -135,7 +135,7 @@ class WebSocketTest extends React.Component<{}, State> {
     });
   };
 
-  testDisconnect = () => {
+  testDisconnect: () => void = () => {
     this._disconnect();
     this._waitFor(this._socketIsDisconnected, 5, disconnectSucceeded => {
       TestModule.markTestPassed(disconnectSucceeded);
diff --git a/Libraries/ActionSheetIOS/NativeActionSheetManager.js b/Libraries/ActionSheetIOS/NativeActionSheetManager.js
index 5f2a1ad0682c4c..28d5d080e82c50 100644
--- a/Libraries/ActionSheetIOS/NativeActionSheetManager.js
+++ b/Libraries/ActionSheetIOS/NativeActionSheetManager.js
@@ -47,4 +47,4 @@ export interface Spec extends TurboModule {
   ) => void;
 }
 
-export default TurboModuleRegistry.get<Spec>('ActionSheetManager');
+export default (TurboModuleRegistry.get<Spec>('ActionSheetManager'): ?Spec);
diff --git a/Libraries/Alert/NativeAlertManager.js b/Libraries/Alert/NativeAlertManager.js
index 1dcae0d265bd17..345fd08c6e65a2 100644
--- a/Libraries/Alert/NativeAlertManager.js
+++ b/Libraries/Alert/NativeAlertManager.js
@@ -31,4 +31,4 @@ export interface Spec extends TurboModule {
   ) => void;
 }
 
-export default TurboModuleRegistry.get<Spec>('AlertManager');
+export default (TurboModuleRegistry.get<Spec>('AlertManager'): ?Spec);
diff --git a/Libraries/Animated/src/AnimatedEvent.js b/Libraries/Animated/src/AnimatedEvent.js
index e06918ce5262e9..8e8c9c24068ce9 100644
--- a/Libraries/Animated/src/AnimatedEvent.js
+++ b/Libraries/Animated/src/AnimatedEvent.js
@@ -14,6 +14,7 @@ const NativeAnimatedHelper = require('./NativeAnimatedHelper');
 const ReactNative = require('../../Renderer/shims/ReactNative');
 
 const invariant = require('invariant');
+
 const {shouldUseNativeDriver} = require('./NativeAnimatedHelper');
 
 export type Mapping = {[key: string]: Mapping} | AnimatedValue;
@@ -26,7 +27,7 @@ function attachNativeEvent(
   viewRef: any,
   eventName: string,
   argMapping: Array<?Mapping>,
-) {
+): $TEMPORARY$object<{|detach: () => void|}> {
   // Find animated values in `argMapping` and create an array representing their
   // key path inside the `nativeEvent` object. Ex.: ['contentOffset', 'x'].
   const eventMappings = [];
@@ -130,7 +131,7 @@ class AnimatedEvent {
     this._attachedEvent && this._attachedEvent.detach();
   }
 
-  __getHandler() {
+  __getHandler(): any | ((...args: any) => void) {
     if (this.__isNative) {
       return this._callListeners;
     }
diff --git a/Libraries/Animated/src/AnimatedWeb.js b/Libraries/Animated/src/AnimatedWeb.js
index 995db03f67b2b6..648c8a0bcccf64 100644
--- a/Libraries/Animated/src/AnimatedWeb.js
+++ b/Libraries/Animated/src/AnimatedWeb.js
@@ -14,7 +14,7 @@ const AnimatedImplementation = require('./AnimatedImplementation');
 
 module.exports = {
   ...AnimatedImplementation,
-  div: AnimatedImplementation.createAnimatedComponent('div'),
-  span: AnimatedImplementation.createAnimatedComponent('span'),
-  img: AnimatedImplementation.createAnimatedComponent('img'),
+  div: (AnimatedImplementation.createAnimatedComponent('div'): $FlowFixMe),
+  span: (AnimatedImplementation.createAnimatedComponent('span'): $FlowFixMe),
+  img: (AnimatedImplementation.createAnimatedComponent('img'): $FlowFixMe),
 };
diff --git a/Libraries/Animated/src/Easing.js b/Libraries/Animated/src/Easing.js
index 423c250fab4935..253a3e785aaa8a 100644
--- a/Libraries/Animated/src/Easing.js
+++ b/Libraries/Animated/src/Easing.js
@@ -61,14 +61,14 @@ class Easing {
   /**
    * A stepping function, returns 1 for any positive value of `n`.
    */
-  static step0(n: number) {
+  static step0(n: number): number {
     return n > 0 ? 1 : 0;
   }
 
   /**
    * A stepping function, returns 1 if `n` is greater than or equal to 1.
    */
-  static step1(n: number) {
+  static step1(n: number): number {
     return n >= 1 ? 1 : 0;
   }
 
@@ -78,7 +78,7 @@ class Easing {
    *
    * http://cubic-bezier.com/#0,0,1,1
    */
-  static linear(t: number) {
+  static linear(t: number): number {
     return t;
   }
 
@@ -101,7 +101,7 @@ class Easing {
    *
    * http://easings.net/#easeInQuad
    */
-  static quad(t: number) {
+  static quad(t: number): number {
     return t * t;
   }
 
@@ -111,7 +111,7 @@ class Easing {
    *
    * http://easings.net/#easeInCubic
    */
-  static cubic(t: number) {
+  static cubic(t: number): number {
     return t * t * t;
   }
 
@@ -121,7 +121,7 @@ class Easing {
    * n = 4: http://easings.net/#easeInQuart
    * n = 5: http://easings.net/#easeInQuint
    */
-  static poly(n: number) {
+  static poly(n: number): (t: number) => number {
     return (t: number) => Math.pow(t, n);
   }
 
@@ -130,7 +130,7 @@ class Easing {
    *
    * http://easings.net/#easeInSine
    */
-  static sin(t: number) {
+  static sin(t: number): number {
     return 1 - Math.cos((t * Math.PI) / 2);
   }
 
@@ -139,7 +139,7 @@ class Easing {
    *
    * http://easings.net/#easeInCirc
    */
-  static circle(t: number) {
+  static circle(t: number): number {
     return 1 - Math.sqrt(1 - t * t);
   }
 
@@ -148,7 +148,7 @@ class Easing {
    *
    * http://easings.net/#easeInExpo
    */
-  static exp(t: number) {
+  static exp(t: number): number {
     return Math.pow(2, 10 * (t - 1));
   }
 
diff --git a/Libraries/Animated/src/NativeAnimatedHelper.js b/Libraries/Animated/src/NativeAnimatedHelper.js
index 4a32be5492dc33..238a8fd2ba9d71 100644
--- a/Libraries/Animated/src/NativeAnimatedHelper.js
+++ b/Libraries/Animated/src/NativeAnimatedHelper.js
@@ -10,17 +10,16 @@
 'use strict';
 
 import NativeEventEmitter from '../../EventEmitter/NativeEventEmitter';
+import type {EventConfig} from './AnimatedEvent';
+import NativeAnimatedModule from './NativeAnimatedModule';
 import type {
   EventMapping,
   AnimatedNodeConfig,
   AnimatingNodeConfig,
 } from './NativeAnimatedModule';
-import NativeAnimatedModule from './NativeAnimatedModule';
-import invariant from 'invariant';
-
 import type {AnimationConfig, EndCallback} from './animations/Animation';
 import type {InterpolationConfigType} from './nodes/AnimatedInterpolation';
-import type {EventConfig} from './AnimatedEvent';
+import invariant from 'invariant';
 
 let __nativeAnimatedNodeTagCount = 1; /* used for animated nodes */
 let __nativeAnimationIdCount = 1; /* used for started animations */
@@ -312,7 +311,7 @@ module.exports = {
   shouldUseNativeDriver,
   transformDataType,
   // $FlowExpectedError - unsafe getter lint suppresion
-  get nativeEventEmitter() {
+  get nativeEventEmitter(): NativeEventEmitter {
     if (!nativeEventEmitter) {
       nativeEventEmitter = new NativeEventEmitter(NativeAnimatedModule);
     }
diff --git a/Libraries/Animated/src/NativeAnimatedModule.js b/Libraries/Animated/src/NativeAnimatedModule.js
index 80ece9d69d04cf..7fcdfc4d871361 100644
--- a/Libraries/Animated/src/NativeAnimatedModule.js
+++ b/Libraries/Animated/src/NativeAnimatedModule.js
@@ -67,4 +67,4 @@ export interface Spec extends TurboModule {
   +removeListeners: (count: number) => void;
 }
 
-export default TurboModuleRegistry.get<Spec>('NativeAnimatedModule');
+export default (TurboModuleRegistry.get<Spec>('NativeAnimatedModule'): ?Spec);
diff --git a/Libraries/Animated/src/animations/DecayAnimation.js b/Libraries/Animated/src/animations/DecayAnimation.js
index a79f9c3ed42912..27ec5d8dd51c54 100644
--- a/Libraries/Animated/src/animations/DecayAnimation.js
+++ b/Libraries/Animated/src/animations/DecayAnimation.js
@@ -13,8 +13,8 @@ const Animation = require('./Animation');
 
 const {shouldUseNativeDriver} = require('../NativeAnimatedHelper');
 
-import type {AnimationConfig, EndCallback} from './Animation';
 import type AnimatedValue from '../nodes/AnimatedValue';
+import type {AnimationConfig, EndCallback} from './Animation';
 
 export type DecayAnimationConfig = AnimationConfig & {
   velocity: number | {x: number, y: number},
@@ -45,7 +45,12 @@ class DecayAnimation extends Animation {
     this.__iterations = config.iterations ?? 1;
   }
 
-  __getNativeAnimationConfig() {
+  __getNativeAnimationConfig(): $TEMPORARY$object<{|
+    deceleration: number,
+    iterations: number,
+    type: $TEMPORARY$string<'decay'>,
+    velocity: number,
+  |}> {
     return {
       type: 'decay',
       deceleration: this._deceleration,
diff --git a/Libraries/Animated/src/animations/SpringAnimation.js b/Libraries/Animated/src/animations/SpringAnimation.js
index a7ffac480ac688..9a16bde6b71c5e 100644
--- a/Libraries/Animated/src/animations/SpringAnimation.js
+++ b/Libraries/Animated/src/animations/SpringAnimation.js
@@ -15,6 +15,7 @@ const Animation = require('./Animation');
 const SpringConfig = require('../SpringConfig');
 
 const invariant = require('invariant');
+
 const {shouldUseNativeDriver} = require('../NativeAnimatedHelper');
 
 import type {AnimationConfig, EndCallback} from './Animation';
@@ -137,7 +138,18 @@ class SpringAnimation extends Animation {
     invariant(this._mass > 0, 'Mass value must be greater than 0');
   }
 
-  __getNativeAnimationConfig() {
+  __getNativeAnimationConfig(): $TEMPORARY$object<{|
+    damping: number,
+    initialVelocity: number,
+    iterations: number,
+    mass: number,
+    overshootClamping: boolean,
+    restDisplacementThreshold: number,
+    restSpeedThreshold: number,
+    stiffness: number,
+    toValue: any,
+    type: $TEMPORARY$string<'spring'>,
+  |}> {
     return {
       type: 'spring',
       overshootClamping: this._overshootClamping,
diff --git a/Libraries/Animated/src/bezier.js b/Libraries/Animated/src/bezier.js
index 727872b848aacd..94fe109d784677 100644
--- a/Libraries/Animated/src/bezier.js
+++ b/Libraries/Animated/src/bezier.js
@@ -84,7 +84,7 @@ module.exports = function bezier(
   mY1: number,
   mX2: number,
   mY2: number,
-) {
+): (x: number) => number {
   if (!(mX1 >= 0 && mX1 <= 1 && mX2 >= 0 && mX2 <= 1)) {
     throw new Error('bezier x values must be in [0, 1] range');
   }
diff --git a/Libraries/Animated/src/components/AnimatedFlatList.js b/Libraries/Animated/src/components/AnimatedFlatList.js
index 9e91e84d9a18d1..2cc3704df4f2e0 100644
--- a/Libraries/Animated/src/components/AnimatedFlatList.js
+++ b/Libraries/Animated/src/components/AnimatedFlatList.js
@@ -14,6 +14,6 @@ const FlatList = require('../../../Lists/FlatList');
 
 const createAnimatedComponent = require('../createAnimatedComponent');
 
-module.exports = createAnimatedComponent(FlatList, {
+module.exports = (createAnimatedComponent(FlatList, {
   scrollEventThrottle: 0.0001,
-});
+}): $FlowFixMe);
diff --git a/Libraries/Animated/src/components/AnimatedImage.js b/Libraries/Animated/src/components/AnimatedImage.js
index 9f5bad944b6eb1..89fee4d29ea8da 100644
--- a/Libraries/Animated/src/components/AnimatedImage.js
+++ b/Libraries/Animated/src/components/AnimatedImage.js
@@ -14,4 +14,4 @@ const Image = require('../../../Image/Image');
 
 const createAnimatedComponent = require('../createAnimatedComponent');
 
-module.exports = createAnimatedComponent(Image);
+module.exports = (createAnimatedComponent(Image): $FlowFixMe);
diff --git a/Libraries/Animated/src/components/AnimatedScrollView.js b/Libraries/Animated/src/components/AnimatedScrollView.js
index 16169dcefe8b2f..5913fb939a159a 100644
--- a/Libraries/Animated/src/components/AnimatedScrollView.js
+++ b/Libraries/Animated/src/components/AnimatedScrollView.js
@@ -14,6 +14,6 @@ const ScrollView = require('../../../Components/ScrollView/ScrollView');
 
 const createAnimatedComponent = require('../createAnimatedComponent');
 
-module.exports = createAnimatedComponent(ScrollView, {
+module.exports = (createAnimatedComponent(ScrollView, {
   scrollEventThrottle: 0.0001,
-});
+}): $FlowFixMe);
diff --git a/Libraries/Animated/src/components/AnimatedSectionList.js b/Libraries/Animated/src/components/AnimatedSectionList.js
index 115e48d443cc3f..6a4a6389fbf668 100644
--- a/Libraries/Animated/src/components/AnimatedSectionList.js
+++ b/Libraries/Animated/src/components/AnimatedSectionList.js
@@ -14,6 +14,6 @@ const SectionList = require('../../../Lists/SectionList');
 
 const createAnimatedComponent = require('../createAnimatedComponent');
 
-module.exports = createAnimatedComponent(SectionList, {
+module.exports = (createAnimatedComponent(SectionList, {
   scrollEventThrottle: 0.0001,
-});
+}): $FlowFixMe);
diff --git a/Libraries/Animated/src/components/AnimatedText.js b/Libraries/Animated/src/components/AnimatedText.js
index 73f9f5e3d68b66..81b016cca18d41 100644
--- a/Libraries/Animated/src/components/AnimatedText.js
+++ b/Libraries/Animated/src/components/AnimatedText.js
@@ -14,4 +14,4 @@ const Text = require('../../../Text/Text');
 
 const createAnimatedComponent = require('../createAnimatedComponent');
 
-module.exports = createAnimatedComponent(Text);
+module.exports = (createAnimatedComponent(Text): $FlowFixMe);
diff --git a/Libraries/Animated/src/components/AnimatedView.js b/Libraries/Animated/src/components/AnimatedView.js
index 6958289d509187..7684dbf3f50da7 100644
--- a/Libraries/Animated/src/components/AnimatedView.js
+++ b/Libraries/Animated/src/components/AnimatedView.js
@@ -14,4 +14,4 @@ const View = require('../../../Components/View/View');
 
 const createAnimatedComponent = require('../createAnimatedComponent');
 
-module.exports = createAnimatedComponent(View);
+module.exports = (createAnimatedComponent(View): $FlowFixMe);
diff --git a/Libraries/AppState/NativeAppState.js b/Libraries/AppState/NativeAppState.js
index ffea188b92bcd0..1146bf588dbbb6 100644
--- a/Libraries/AppState/NativeAppState.js
+++ b/Libraries/AppState/NativeAppState.js
@@ -27,4 +27,4 @@ export interface Spec extends TurboModule {
   +removeListeners: (count: number) => void;
 }
 
-export default TurboModuleRegistry.getEnforcing<Spec>('AppState');
+export default (TurboModuleRegistry.getEnforcing<Spec>('AppState'): Spec);
diff --git a/Libraries/BatchedBridge/BatchedBridge.js b/Libraries/BatchedBridge/BatchedBridge.js
index 5cd0138b48e131..b68e9873e393ba 100644
--- a/Libraries/BatchedBridge/BatchedBridge.js
+++ b/Libraries/BatchedBridge/BatchedBridge.js
@@ -12,7 +12,7 @@
 
 const MessageQueue = require('./MessageQueue');
 
-const BatchedBridge = new MessageQueue();
+const BatchedBridge: MessageQueue = new MessageQueue();
 
 // Wire up the batched bridge on the global object so that we can call into it.
 // Ideally, this would be the inverse relationship. I.e. the native environment
diff --git a/Libraries/BatchedBridge/MessageQueue.js b/Libraries/BatchedBridge/MessageQueue.js
index b12295e840cf30..260a38f297dd15 100644
--- a/Libraries/BatchedBridge/MessageQueue.js
+++ b/Libraries/BatchedBridge/MessageQueue.js
@@ -101,7 +101,11 @@ class MessageQueue {
     }
   }
 
-  callFunctionReturnFlushedQueue(module: string, method: string, args: any[]) {
+  callFunctionReturnFlushedQueue(
+    module: string,
+    method: string,
+    args: any[],
+  ): null | [Array<number>, Array<number>, Array<any>, number] {
     this.__guard(() => {
       this.__callFunction(module, method, args);
     });
@@ -113,7 +117,7 @@ class MessageQueue {
     module: string,
     method: string,
     args: any[],
-  ) {
+  ): $TEMPORARY$array<?[Array<number>, Array<number>, Array<any>, number]> {
     let result;
     this.__guard(() => {
       result = this.__callFunction(module, method, args);
@@ -122,7 +126,10 @@ class MessageQueue {
     return [result, this.flushedQueue()];
   }
 
-  invokeCallbackAndReturnFlushedQueue(cbID: number, args: any[]) {
+  invokeCallbackAndReturnFlushedQueue(
+    cbID: number,
+    args: any[],
+  ): null | [Array<number>, Array<number>, Array<any>, number] {
     this.__guard(() => {
       this.__invokeCallback(cbID, args);
     });
@@ -130,7 +137,7 @@ class MessageQueue {
     return this.flushedQueue();
   }
 
-  flushedQueue() {
+  flushedQueue(): null | [Array<number>, Array<number>, Array<any>, number] {
     this.__guard(() => {
       this.__callImmediates();
     });
@@ -140,7 +147,7 @@ class MessageQueue {
     return queue[0].length ? queue : null;
   }
 
-  getEventLoopRunningTime() {
+  getEventLoopRunningTime(): number {
     return Date.now() - this._eventLoopStartTime;
   }
 
@@ -160,7 +167,7 @@ class MessageQueue {
     };
   }
 
-  getCallableModule(name: string) {
+  getCallableModule(name: string): any | null {
     const getValue = this._lazyCallableModules[name];
     return getValue ? getValue() : null;
   }
@@ -171,7 +178,7 @@ class MessageQueue {
     params: any[],
     onFail: ?Function,
     onSucc: ?Function,
-  ) {
+  ): any {
     if (__DEV__) {
       invariant(
         global.nativeCallSyncHook,
@@ -383,7 +390,7 @@ class MessageQueue {
   // This makes stacktraces to be placed at MessageQueue rather than at where they were launched
   // The parameter DebuggerInternal.shouldPauseOnThrow is used to check before catching all exceptions and
   // can be configured by the VM or any Inspector
-  __shouldPauseOnThrow() {
+  __shouldPauseOnThrow(): boolean {
     return (
       // $FlowFixMe
       typeof DebuggerInternal !== 'undefined' &&
diff --git a/Libraries/Blob/BlobManager.js b/Libraries/Blob/BlobManager.js
index 9176218373ca67..e12512392a3e78 100644
--- a/Libraries/Blob/BlobManager.js
+++ b/Libraries/Blob/BlobManager.js
@@ -12,10 +12,10 @@
 
 const Blob = require('./Blob');
 const BlobRegistry = require('./BlobRegistry');
-import NativeBlobModule from './NativeBlobModule';
-import invariant from 'invariant';
 
 import type {BlobData, BlobOptions, BlobCollector} from './BlobTypes';
+import NativeBlobModule from './NativeBlobModule';
+import invariant from 'invariant';
 
 /*eslint-disable no-bitwise */
 /*eslint-disable eqeqeq */
@@ -54,7 +54,7 @@ class BlobManager {
   /**
    * If the native blob module is available.
    */
-  static isAvailable = !!NativeBlobModule;
+  static isAvailable: boolean = !!NativeBlobModule;
 
   /**
    * Create blob from existing array of blobs.
diff --git a/Libraries/Blob/BlobRegistry.js b/Libraries/Blob/BlobRegistry.js
index cfd0475a53ea07..f3cd13ebc48fbb 100644
--- a/Libraries/Blob/BlobRegistry.js
+++ b/Libraries/Blob/BlobRegistry.js
@@ -27,7 +27,7 @@ const unregister = (id: string) => {
   }
 };
 
-const has = (id: string) => {
+const has = (id: string): number | boolean => {
   return registry[id] && registry[id] > 0;
 };
 
diff --git a/Libraries/Blob/FileReader.js b/Libraries/Blob/FileReader.js
index b9113966f1a9fb..fc769f8a544a72 100644
--- a/Libraries/Blob/FileReader.js
+++ b/Libraries/Blob/FileReader.js
@@ -10,8 +10,9 @@
 
 'use strict';
 
-const EventTarget = require('event-target-shim');
 const Blob = require('./Blob');
+const EventTarget = require('event-target-shim');
+
 import NativeFileReaderModule from './NativeFileReaderModule';
 
 type ReadyState =
@@ -34,14 +35,14 @@ const EMPTY = 0;
 const LOADING = 1;
 const DONE = 2;
 
-class FileReader extends EventTarget(...READER_EVENTS) {
-  static EMPTY = EMPTY;
-  static LOADING = LOADING;
-  static DONE = DONE;
+class FileReader extends (EventTarget(...READER_EVENTS): any) {
+  static EMPTY: number = EMPTY;
+  static LOADING: number = LOADING;
+  static DONE: number = DONE;
 
-  EMPTY = EMPTY;
-  LOADING = LOADING;
-  DONE = DONE;
+  EMPTY: number = EMPTY;
+  LOADING: number = LOADING;
+  DONE: number = DONE;
 
   _readyState: ReadyState;
   _error: ?Error;
diff --git a/Libraries/Blob/NativeBlobModule.js b/Libraries/Blob/NativeBlobModule.js
index cb44600c642ae6..2949b755951b5a 100644
--- a/Libraries/Blob/NativeBlobModule.js
+++ b/Libraries/Blob/NativeBlobModule.js
@@ -23,4 +23,4 @@ export interface Spec extends TurboModule {
   +release: (blobId: string) => void;
 }
 
-export default TurboModuleRegistry.get<Spec>('BlobModule');
+export default (TurboModuleRegistry.get<Spec>('BlobModule'): ?Spec);
diff --git a/Libraries/Blob/NativeFileReaderModule.js b/Libraries/Blob/NativeFileReaderModule.js
index 2291c2e60ad21f..ac135db7394d19 100644
--- a/Libraries/Blob/NativeFileReaderModule.js
+++ b/Libraries/Blob/NativeFileReaderModule.js
@@ -18,4 +18,6 @@ export interface Spec extends TurboModule {
   +readAsText: (data: Object, encoding: string) => Promise<string>;
 }
 
-export default TurboModuleRegistry.getEnforcing<Spec>('FileReaderModule');
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'FileReaderModule',
+): Spec);
diff --git a/Libraries/Blob/__mocks__/FileReaderModule.js b/Libraries/Blob/__mocks__/FileReaderModule.js
index da687eca470b1d..a3cdbf6848cd1a 100644
--- a/Libraries/Blob/__mocks__/FileReaderModule.js
+++ b/Libraries/Blob/__mocks__/FileReaderModule.js
@@ -8,10 +8,10 @@
  * @format
  */
 const FileReaderModule = {
-  async readAsText() {
+  async readAsText(): Promise<string> {
     return '';
   },
-  async readAsDataURL() {
+  async readAsDataURL(): Promise<string> {
     return 'data:text/plain;base64,NDI=';
   },
 };
diff --git a/Libraries/BugReporting/dumpReactTree.js b/Libraries/BugReporting/dumpReactTree.js
index 2ef17ecf034784..0960662911cc3a 100644
--- a/Libraries/BugReporting/dumpReactTree.js
+++ b/Libraries/BugReporting/dumpReactTree.js
@@ -23,7 +23,7 @@ const MAX_STRING_LENGTH = 50;
  * it best to get the content but ultimately relies on implementation details
  * of React and will fail in future versions.
  */
-function dumpReactTree() {
+function dumpReactTree(): string {
   try {
     return getReactTree();
   } catch (e) {
diff --git a/Libraries/Components/AccessibilityInfo/AccessibilityInfo.ios.js b/Libraries/Components/AccessibilityInfo/AccessibilityInfo.ios.js
index a804af6fd68dd0..9a86653d452849 100644
--- a/Libraries/Components/AccessibilityInfo/AccessibilityInfo.ios.js
+++ b/Libraries/Components/AccessibilityInfo/AccessibilityInfo.ios.js
@@ -10,11 +10,11 @@
 
 'use strict';
 
-import NativeAccessibilityManager from './NativeAccessibilityManager';
-
 const Promise = require('../../Promise');
 const RCTDeviceEventEmitter = require('../../EventEmitter/RCTDeviceEventEmitter');
 
+import NativeAccessibilityManager from './NativeAccessibilityManager';
+
 const CHANGE_EVENT_NAME = {
   announcementFinished: 'announcementFinished',
   boldTextChanged: 'boldTextChanged',
@@ -164,7 +164,7 @@ const AccessibilityInfo = {
    *
    * Same as `isScreenReaderEnabled`
    */
-  get fetch() {
+  get fetch(): $FlowFixMe {
     return this.isScreenReaderEnabled;
   },
 
diff --git a/Libraries/Components/AccessibilityInfo/NativeAccessibilityInfo.js b/Libraries/Components/AccessibilityInfo/NativeAccessibilityInfo.js
index 2f51c3c183de30..ef2b968652082c 100644
--- a/Libraries/Components/AccessibilityInfo/NativeAccessibilityInfo.js
+++ b/Libraries/Components/AccessibilityInfo/NativeAccessibilityInfo.js
@@ -24,4 +24,4 @@ export interface Spec extends TurboModule {
   +announceForAccessibility: (announcement: string) => void;
 }
 
-export default TurboModuleRegistry.get<Spec>('AccessibilityInfo');
+export default (TurboModuleRegistry.get<Spec>('AccessibilityInfo'): ?Spec);
diff --git a/Libraries/Components/AccessibilityInfo/NativeAccessibilityManager.js b/Libraries/Components/AccessibilityInfo/NativeAccessibilityManager.js
index b0fe8dd1d7ed70..8122934edcd4af 100644
--- a/Libraries/Components/AccessibilityInfo/NativeAccessibilityManager.js
+++ b/Libraries/Components/AccessibilityInfo/NativeAccessibilityManager.js
@@ -42,4 +42,4 @@ export interface Spec extends TurboModule {
   +announceForAccessibility: (announcement: string) => void;
 }
 
-export default TurboModuleRegistry.get<Spec>('AccessibilityManager');
+export default (TurboModuleRegistry.get<Spec>('AccessibilityManager'): ?Spec);
diff --git a/Libraries/Components/AppleTV/NativeTVNavigationEventEmitter.js b/Libraries/Components/AppleTV/NativeTVNavigationEventEmitter.js
index 27f33bd7270df2..97edfcdf99c5d3 100644
--- a/Libraries/Components/AppleTV/NativeTVNavigationEventEmitter.js
+++ b/Libraries/Components/AppleTV/NativeTVNavigationEventEmitter.js
@@ -18,4 +18,6 @@ export interface Spec extends TurboModule {
   +removeListeners: (count: number) => void;
 }
 
-export default TurboModuleRegistry.get<Spec>('TVNavigationEventEmitter');
+export default (TurboModuleRegistry.get<Spec>(
+  'TVNavigationEventEmitter',
+): ?Spec);
diff --git a/Libraries/Components/Clipboard/NativeClipboard.js b/Libraries/Components/Clipboard/NativeClipboard.js
index 002a7ebb2e9f8e..93fc92873eecda 100644
--- a/Libraries/Components/Clipboard/NativeClipboard.js
+++ b/Libraries/Components/Clipboard/NativeClipboard.js
@@ -19,4 +19,4 @@ export interface Spec extends TurboModule {
   +setString: (content: string) => void;
 }
 
-export default TurboModuleRegistry.getEnforcing<Spec>('Clipboard');
+export default (TurboModuleRegistry.getEnforcing<Spec>('Clipboard'): Spec);
diff --git a/Libraries/Components/DatePicker/DatePickerIOS.ios.js b/Libraries/Components/DatePicker/DatePickerIOS.ios.js
index 9550619e9eb096..c01a3c495dd664 100644
--- a/Libraries/Components/DatePicker/DatePickerIOS.ios.js
+++ b/Libraries/Components/DatePicker/DatePickerIOS.ios.js
@@ -13,16 +13,15 @@
 
 'use strict';
 
+const RCTDatePickerNativeComponent = require('./RCTDatePickerNativeComponent');
 const React = require('react');
 const StyleSheet = require('../../StyleSheet/StyleSheet');
 const View = require('../View/View');
 
 const invariant = require('invariant');
 
-import type {ViewProps} from '../View/ViewPropTypes';
 import type {SyntheticEvent} from '../../Types/CoreEventTypes';
-
-const RCTDatePickerNativeComponent = require('./RCTDatePickerNativeComponent');
+import type {ViewProps} from '../View/ViewPropTypes';
 
 type Event = SyntheticEvent<
   $ReadOnly<{|
@@ -113,7 +112,9 @@ type Props = $ReadOnly<{|
  * source of truth.
  */
 class DatePickerIOS extends React.Component<Props> {
-  static DefaultProps = {
+  static DefaultProps: $TEMPORARY$object<{|
+    mode: $TEMPORARY$string<'datetime'>,
+  |}> = {
     mode: 'datetime',
   };
 
@@ -137,7 +138,7 @@ class DatePickerIOS extends React.Component<Props> {
     this.props.onChange && this.props.onChange(event);
   };
 
-  render() {
+  render(): React.Node {
     const props = this.props;
     invariant(
       props.date || props.initialDate,
diff --git a/Libraries/Components/DatePickerAndroid/NativeDatePickerAndroid.js b/Libraries/Components/DatePickerAndroid/NativeDatePickerAndroid.js
index a0676f033291b5..778befa4ebc84a 100644
--- a/Libraries/Components/DatePickerAndroid/NativeDatePickerAndroid.js
+++ b/Libraries/Components/DatePickerAndroid/NativeDatePickerAndroid.js
@@ -17,4 +17,6 @@ export interface Spec extends TurboModule {
   +open: (options: Object) => Promise<Object>;
 }
 
-export default TurboModuleRegistry.getEnforcing<Spec>('DatePickerAndroid');
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'DatePickerAndroid',
+): Spec);
diff --git a/Libraries/Components/DrawerAndroid/AndroidDrawerLayoutNativeComponent.js b/Libraries/Components/DrawerAndroid/AndroidDrawerLayoutNativeComponent.js
index 9507b691b58645..778b609fc29103 100644
--- a/Libraries/Components/DrawerAndroid/AndroidDrawerLayoutNativeComponent.js
+++ b/Libraries/Components/DrawerAndroid/AndroidDrawerLayoutNativeComponent.js
@@ -10,17 +10,17 @@
 
 'use strict';
 
-import codegenNativeCommands from 'react-native/Libraries/Utilities/codegenNativeCommands';
-import codegenNativeComponent from 'react-native/Libraries/Utilities/codegenNativeComponent';
-import * as React from 'react';
 import type {ViewProps} from 'react-native/Libraries/Components/View/ViewPropTypes';
+import type {ColorValue} from 'react-native/Libraries/StyleSheet/StyleSheetTypes';
 import type {
   WithDefault,
   DirectEventHandler,
   Int32,
   Float,
 } from 'react-native/Libraries/Types/CodegenTypes';
-import type {ColorValue} from 'react-native/Libraries/StyleSheet/StyleSheetTypes';
+import codegenNativeCommands from 'react-native/Libraries/Utilities/codegenNativeCommands';
+import codegenNativeComponent from 'react-native/Libraries/Utilities/codegenNativeComponent';
+import * as React from 'react';
 
 type DrawerStateEvent = $ReadOnly<{|
   drawerState: Int32,
@@ -113,7 +113,7 @@ type NativeProps = $ReadOnly<{|
   statusBarBackgroundColor?: ?ColorValue,
 |}>;
 
-export const Commands = codegenNativeCommands<NativeCommands>({
+export const Commands: NativeCommands = codegenNativeCommands<NativeCommands>({
   supportedCommands: ['openDrawer', 'closeDrawer'],
 });
 
diff --git a/Libraries/Components/Keyboard/Keyboard.js b/Libraries/Components/Keyboard/Keyboard.js
index 976aab0aa7daaf..a024a447861bcd 100644
--- a/Libraries/Components/Keyboard/Keyboard.js
+++ b/Libraries/Components/Keyboard/Keyboard.js
@@ -11,9 +11,10 @@
 'use strict';
 
 const LayoutAnimation = require('../../LayoutAnimation/LayoutAnimation');
-const invariant = require('invariant');
 const NativeEventEmitter = require('../../EventEmitter/NativeEventEmitter');
+
 const dismissKeyboard = require('../../Utilities/dismissKeyboard');
+const invariant = require('invariant');
 
 import NativeKeyboardObserver from './NativeKeyboardObserver';
 const KeyboardEventEmitter = new NativeEventEmitter(NativeKeyboardObserver);
@@ -108,7 +109,21 @@ type KeyboardEventListener = (e: KeyboardEvent) => void;
  *```
  */
 
-let Keyboard = {
+let Keyboard:
+  | NativeEventEmitter
+  | $TEMPORARY$object<{|
+      addListener: (
+        eventName: KeyboardEventName,
+        callback: KeyboardEventListener,
+      ) => $FlowFixMe,
+      dismiss: () => $FlowFixMe,
+      removeAllListeners: (eventName: KeyboardEventName) => $FlowFixMe,
+      removeListener: (
+        eventName: KeyboardEventName,
+        callback: KeyboardEventListener,
+      ) => $FlowFixMe,
+      scheduleLayoutAnimation: (event: KeyboardEvent) => $FlowFixMe,
+    |}> = {
   /**
    * The `addListener` function connects a JavaScript function to an identified native
    * keyboard notification event.
diff --git a/Libraries/Components/Keyboard/KeyboardAvoidingView.js b/Libraries/Components/Keyboard/KeyboardAvoidingView.js
index 9f9bbbfc608185..ae0dd37fb0814c 100644
--- a/Libraries/Components/Keyboard/KeyboardAvoidingView.js
+++ b/Libraries/Components/Keyboard/KeyboardAvoidingView.js
@@ -17,8 +17,8 @@ const React = require('react');
 const StyleSheet = require('../../StyleSheet/StyleSheet');
 const View = require('../View/View');
 
-import type EmitterSubscription from '../../vendor/emitter/EmitterSubscription';
 import type {ViewStyleProp} from '../../StyleSheet/StyleSheet';
+import type EmitterSubscription from '../../vendor/emitter/EmitterSubscription';
 import type {
   ViewProps,
   ViewLayout,
@@ -61,7 +61,10 @@ type State = {|
  * adjusting its height, position, or bottom padding.
  */
 class KeyboardAvoidingView extends React.Component<Props, State> {
-  static defaultProps = {
+  static defaultProps: $TEMPORARY$object<{|
+    enabled: boolean,
+    keyboardVerticalOffset: number,
+  |}> = {
     enabled: true,
     keyboardVerticalOffset: 0,
   };
diff --git a/Libraries/Components/Keyboard/NativeKeyboardObserver.js b/Libraries/Components/Keyboard/NativeKeyboardObserver.js
index 04d95a6b69b292..e26598dd4cec3e 100644
--- a/Libraries/Components/Keyboard/NativeKeyboardObserver.js
+++ b/Libraries/Components/Keyboard/NativeKeyboardObserver.js
@@ -18,4 +18,4 @@ export interface Spec extends TurboModule {
   +removeListeners: (count: number) => void;
 }
 
-export default TurboModuleRegistry.get<Spec>('KeyboardObserver');
+export default (TurboModuleRegistry.get<Spec>('KeyboardObserver'): ?Spec);
diff --git a/Libraries/Components/MaskedView/MaskedViewIOS.ios.js b/Libraries/Components/MaskedView/MaskedViewIOS.ios.js
index 7caff48178c768..4a32d29836f8d0 100644
--- a/Libraries/Components/MaskedView/MaskedViewIOS.ios.js
+++ b/Libraries/Components/MaskedView/MaskedViewIOS.ios.js
@@ -11,9 +11,9 @@
 const React = require('react');
 const StyleSheet = require('../../StyleSheet/StyleSheet');
 const View = require('../View/View');
-import RCTMaskedViewNativeComponent from './RCTMaskedViewNativeComponent';
 
 import type {ViewProps} from '../View/ViewPropTypes';
+import RCTMaskedViewNativeComponent from './RCTMaskedViewNativeComponent';
 
 type Props = $ReadOnly<{|
   ...ViewProps,
@@ -65,7 +65,7 @@ type Props = $ReadOnly<{|
 class MaskedViewIOS extends React.Component<Props> {
   _hasWarnedInvalidRenderMask = false;
 
-  render() {
+  render(): React.Node {
     const {maskElement, children, ...otherViewProps} = this.props;
 
     if (!React.isValidElement(maskElement)) {
diff --git a/Libraries/Components/Picker/Picker.js b/Libraries/Components/Picker/Picker.js
index 5353986959f686..cded08c74d8d15 100644
--- a/Libraries/Components/Picker/Picker.js
+++ b/Libraries/Components/Picker/Picker.js
@@ -121,20 +121,22 @@ class Picker extends React.Component<PickerProps> {
   /**
    * On Android, display the options in a dialog.
    */
-  static MODE_DIALOG = MODE_DIALOG;
+  static MODE_DIALOG: $TEMPORARY$string<'dialog'> = MODE_DIALOG;
 
   /**
    * On Android, display the options in a dropdown (this is the default).
    */
-  static MODE_DROPDOWN = MODE_DROPDOWN;
+  static MODE_DROPDOWN: $TEMPORARY$string<'dropdown'> = MODE_DROPDOWN;
 
-  static Item = PickerItem;
+  static Item: typeof PickerItem = PickerItem;
 
-  static defaultProps = {
+  static defaultProps: $TEMPORARY$object<{|
+    mode: $TEMPORARY$string<'dialog'>,
+  |}> = {
     mode: MODE_DIALOG,
   };
 
-  render() {
+  render(): React.Node {
     if (Platform.OS === 'ios') {
       /* $FlowFixMe(>=0.81.0 site=react_native_ios_fb) This suppression was
        * added when renaming suppression sites. */
diff --git a/Libraries/Components/Picker/PickerIOS.ios.js b/Libraries/Components/Picker/PickerIOS.ios.js
index 382b6df6153982..7a642f97120d1d 100644
--- a/Libraries/Components/Picker/PickerIOS.ios.js
+++ b/Libraries/Components/Picker/PickerIOS.ios.js
@@ -13,17 +13,18 @@
 
 'use strict';
 
+const RCTPickerNativeComponent = require('./RCTPickerNativeComponent');
 const React = require('react');
 const ReactNative = require('../../Renderer/shims/ReactNative');
 const StyleSheet = require('../../StyleSheet/StyleSheet');
 const View = require('../View/View');
+
 const processColor = require('../../StyleSheet/processColor');
-const RCTPickerNativeComponent = require('./RCTPickerNativeComponent');
 
-import type {SyntheticEvent} from '../../Types/CoreEventTypes';
+import type {TextStyleProp} from '../../StyleSheet/StyleSheet';
 import type {ColorValue} from '../../StyleSheet/StyleSheetTypes';
+import type {SyntheticEvent} from '../../Types/CoreEventTypes';
 import type {ViewProps} from '../View/ViewPropTypes';
-import type {TextStyleProp} from '../../StyleSheet/StyleSheet';
 
 type PickerIOSChangeEvent = SyntheticEvent<
   $ReadOnly<{|
@@ -74,19 +75,19 @@ type ItemProps = $ReadOnly<{|
   color?: ?ColorValue,
 |}>;
 
-const PickerIOSItem = (props: ItemProps) => {
+const PickerIOSItem = (props: ItemProps): null => {
   return null;
 };
 
 class PickerIOS extends React.Component<Props, State> {
   _picker: ?React.ElementRef<RCTPickerIOSType> = null;
 
-  state = {
+  state: State = {
     selectedIndex: 0,
     items: [],
   };
 
-  static Item = PickerIOSItem;
+  static Item: (props: ItemProps) => null = PickerIOSItem;
 
   static getDerivedStateFromProps(props: Props): State {
     let selectedIndex = 0;
@@ -106,7 +107,7 @@ class PickerIOS extends React.Component<Props, State> {
     return {selectedIndex, items};
   }
 
-  render() {
+  render(): React.Node {
     return (
       <View style={this.props.style}>
         <RCTPickerNativeComponent
diff --git a/Libraries/Components/RefreshControl/__mocks__/RefreshControlMock.js b/Libraries/Components/RefreshControl/__mocks__/RefreshControlMock.js
index f0c6e5c467fc62..1ca76f7f2d17b3 100644
--- a/Libraries/Components/RefreshControl/__mocks__/RefreshControlMock.js
+++ b/Libraries/Components/RefreshControl/__mocks__/RefreshControlMock.js
@@ -21,7 +21,7 @@ class RefreshControlMock extends React.Component<{}> {
   componentDidMount() {
     RefreshControlMock.latestRef = this;
   }
-  render() {
+  render(): React.Element<string> {
     return <RCTRefreshControl />;
   }
 }
diff --git a/Libraries/Components/SafeAreaView/SafeAreaView.js b/Libraries/Components/SafeAreaView/SafeAreaView.js
index 61be02b030ea1b..a6d7afc1b97492 100644
--- a/Libraries/Components/SafeAreaView/SafeAreaView.js
+++ b/Libraries/Components/SafeAreaView/SafeAreaView.js
@@ -12,15 +12,15 @@ const Platform = require('../../Utilities/Platform');
 const React = require('react');
 const View = require('../View/View');
 
-import type {ViewProps} from '../View/ViewPropTypes';
 import type {NativeComponent} from '../../Renderer/shims/ReactNative';
+import type {ViewProps} from '../View/ViewPropTypes';
 
 type Props = $ReadOnly<{|
   ...ViewProps,
   emulateUnlessSupported?: boolean,
 |}>;
 
-let exported;
+let exported: Class<React$Component<Props>> | Class<NativeComponent<Props>>;
 
 /**
  * Renders nested content and automatically applies paddings reflect the portion
diff --git a/Libraries/Components/ScrollView/ScrollView.js b/Libraries/Components/ScrollView/ScrollView.js
index a16c4b49d23e58..b4298158b3354f 100644
--- a/Libraries/Components/ScrollView/ScrollView.js
+++ b/Libraries/Components/ScrollView/ScrollView.js
@@ -27,21 +27,20 @@ const requireNativeComponent = require('../../ReactNative/requireNativeComponent
 const resolveAssetSource = require('../../Image/resolveAssetSource');
 const splitLayoutProps = require('../../StyleSheet/splitLayoutProps');
 
+import type {NativeMethodsMixinType} from '../../Renderer/shims/ReactNativeTypes';
+import type {EdgeInsetsProp} from '../../StyleSheet/EdgeInsetsPropType';
+import type {PointProp} from '../../StyleSheet/PointPropType';
+import type {ViewStyleProp} from '../../StyleSheet/StyleSheet';
+import type {ColorValue} from '../../StyleSheet/StyleSheetTypes';
 import type {
   PressEvent,
   ScrollEvent,
   LayoutEvent,
 } from '../../Types/CoreEventTypes';
-import type {EdgeInsetsProp} from '../../StyleSheet/EdgeInsetsPropType';
-import type {NativeMethodsMixinType} from '../../Renderer/shims/ReactNativeTypes';
-import type {ViewStyleProp} from '../../StyleSheet/StyleSheet';
+import type {State as ScrollResponderState} from '../ScrollResponder';
 import type {ViewProps} from '../View/ViewPropTypes';
-import type {PointProp} from '../../StyleSheet/PointPropType';
 import type {Props as ScrollViewStickyHeaderProps} from './ScrollViewStickyHeader';
 
-import type {ColorValue} from '../../StyleSheet/StyleSheetTypes';
-import type {State as ScrollResponderState} from '../ScrollResponder';
-
 let AndroidScrollView;
 let AndroidHorizontalScrollContentView;
 let AndroidHorizontalScrollView;
@@ -628,7 +627,7 @@ const standardVerticalContext: ContextType = Object.freeze({horizontal: false});
  * supports out of the box.
  */
 class ScrollView extends React.Component<Props, State> {
-  static Context = Context;
+  static Context: React$Context<ContextType> = Context;
   /**
    * Part 1: Removing ScrollResponder.Mixin:
    *
@@ -688,7 +687,7 @@ class ScrollView extends React.Component<Props, State> {
   _stickyHeaderRefs: Map<string, StickyHeaderComponentType> = new Map();
   _headerLayoutYs: Map<string, number> = new Map();
 
-  state = {
+  state: State = {
     layoutHeight: null,
     ...ScrollResponder.Mixin.scrollResponderMixinGetInitialState(),
   };
@@ -941,7 +940,7 @@ class ScrollView extends React.Component<Props, State> {
     this._innerViewRef = ref;
   };
 
-  render() {
+  render(): React.Node | React.Element<string> {
     let ScrollViewClass;
     let ScrollContentContainerViewClass;
     if (Platform.OS === 'android') {
diff --git a/Libraries/Components/ScrollView/ScrollViewStickyHeader.js b/Libraries/Components/ScrollView/ScrollViewStickyHeader.js
index 702d23667f98b0..c9a967f9c85602 100644
--- a/Libraries/Components/ScrollView/ScrollViewStickyHeader.js
+++ b/Libraries/Components/ScrollView/ScrollViewStickyHeader.js
@@ -38,7 +38,7 @@ type State = {
 };
 
 class ScrollViewStickyHeader extends React.Component<Props, State> {
-  state = {
+  state: State = {
     measured: false,
     layoutY: 0,
     layoutHeight: 0,
@@ -63,7 +63,7 @@ class ScrollViewStickyHeader extends React.Component<Props, State> {
     }
   };
 
-  render() {
+  render(): React.Node {
     const {inverted, scrollViewHeight} = this.props;
     const {measured, layoutHeight, layoutY, nextHeaderLayoutY} = this.state;
     const inputRange: Array<number> = [-1, 0];
diff --git a/Libraries/Components/ScrollView/__mocks__/ScrollViewMock.js b/Libraries/Components/ScrollView/__mocks__/ScrollViewMock.js
index 85195684ca7cca..7360b7778dcaff 100644
--- a/Libraries/Components/ScrollView/__mocks__/ScrollViewMock.js
+++ b/Libraries/Components/ScrollView/__mocks__/ScrollViewMock.js
@@ -19,10 +19,10 @@ const requireNativeComponent = require('../../../ReactNative/requireNativeCompon
 
 const RCTScrollView = requireNativeComponent('RCTScrollView');
 
-const ScrollViewComponent = jest.genMockFromModule('../ScrollView');
+const ScrollViewComponent: $FlowFixMe = jest.genMockFromModule('../ScrollView');
 
 class ScrollViewMock extends ScrollViewComponent {
-  render() {
+  render(): React.Element<string> {
     return (
       <RCTScrollView {...this.props}>
         {this.props.refreshControl}
diff --git a/Libraries/Components/Sound/NativeSoundManager.js b/Libraries/Components/Sound/NativeSoundManager.js
index 4858305cadef3b..80ba8743fde455 100644
--- a/Libraries/Components/Sound/NativeSoundManager.js
+++ b/Libraries/Components/Sound/NativeSoundManager.js
@@ -20,4 +20,4 @@ export interface Spec extends TurboModule {
   +playTouchSound: () => void;
 }
 
-export default TurboModuleRegistry.getEnforcing<Spec>('SoundManager');
+export default (TurboModuleRegistry.getEnforcing<Spec>('SoundManager'): Spec);
diff --git a/Libraries/Components/StaticContainer.react.js b/Libraries/Components/StaticContainer.react.js
index 948e16ef85c5c0..aab461272d19ff 100644
--- a/Libraries/Components/StaticContainer.react.js
+++ b/Libraries/Components/StaticContainer.react.js
@@ -43,7 +43,7 @@ class StaticContainer extends React.Component<Props> {
     return !!nextProps.shouldUpdate;
   }
 
-  render() {
+  render(): null | React$Node {
     const child = this.props.children;
     return child === null || child === false
       ? null
diff --git a/Libraries/Components/StatusBar/NativeStatusBarManager.js b/Libraries/Components/StatusBar/NativeStatusBarManager.js
index 4c7337ad9d2f7f..9743d22275894f 100644
--- a/Libraries/Components/StatusBar/NativeStatusBarManager.js
+++ b/Libraries/Components/StatusBar/NativeStatusBarManager.js
@@ -45,4 +45,6 @@ export interface Spec extends TurboModule {
   +setHidden: (hidden: boolean, withAnimation?: ?string) => void;
 }
 
-export default TurboModuleRegistry.getEnforcing<Spec>('StatusBarManager');
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'StatusBarManager',
+): Spec);
diff --git a/Libraries/Components/StatusBar/StatusBar.js b/Libraries/Components/StatusBar/StatusBar.js
index cb4a8f74e88431..4d50ce488015b4 100644
--- a/Libraries/Components/StatusBar/StatusBar.js
+++ b/Libraries/Components/StatusBar/StatusBar.js
@@ -10,10 +10,11 @@
 
 'use strict';
 
-const React = require('react');
 const Platform = require('../../Utilities/Platform');
+const React = require('react');
 
 const processColor = require('../../StyleSheet/processColor');
+
 import NativeStatusBarManager from './NativeStatusBarManager';
 
 /**
@@ -245,7 +246,7 @@ class StatusBar extends React.Component<Props> {
    *
    * @platform android
    */
-  static currentHeight = NativeStatusBarManager.getConstants().HEIGHT;
+  static currentHeight: number = NativeStatusBarManager.getConstants().HEIGHT;
 
   // Provide an imperative API as static functions of the component.
   // See the corresponding prop for more detail.
@@ -339,7 +340,7 @@ class StatusBar extends React.Component<Props> {
    *
    * @param props Object containing the StatusBar props to use in the stack entry.
    */
-  static pushStackEntry(props: any) {
+  static pushStackEntry(props: any): any {
     const entry = createStackEntry(props);
     StatusBar._propsStack.push(entry);
     StatusBar._updatePropsStack();
@@ -365,7 +366,7 @@ class StatusBar extends React.Component<Props> {
    * @param entry Entry returned from `pushStackEntry` to replace.
    * @param props Object containing the StatusBar props to use in the replacement stack entry.
    */
-  static replaceStackEntry(entry: any, props: any) {
+  static replaceStackEntry(entry: any, props: any): any {
     const newEntry = createStackEntry(props);
     const index = StatusBar._propsStack.indexOf(entry);
     if (index !== -1) {
@@ -375,7 +376,10 @@ class StatusBar extends React.Component<Props> {
     return newEntry;
   }
 
-  static defaultProps = {
+  static defaultProps: $TEMPORARY$object<{|
+    animated: boolean,
+    showHideTransition: $TEMPORARY$string<'fade'>,
+  |}> = {
     animated: false,
     showHideTransition: 'fade',
   };
diff --git a/Libraries/Components/StatusBar/StatusBarIOS.ios.js b/Libraries/Components/StatusBar/StatusBarIOS.ios.js
index de852f8de4f058..f3ebbf4d98824c 100644
--- a/Libraries/Components/StatusBar/StatusBarIOS.ios.js
+++ b/Libraries/Components/StatusBar/StatusBarIOS.ios.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const NativeEventEmitter = require('../../EventEmitter/NativeEventEmitter');
+
 import NativeStatusBarManager from './NativeStatusBarManager';
 
 /**
@@ -18,4 +19,4 @@ import NativeStatusBarManager from './NativeStatusBarManager';
  */
 class StatusBarIOS extends NativeEventEmitter {}
 
-module.exports = new StatusBarIOS(NativeStatusBarManager);
+module.exports = (new StatusBarIOS(NativeStatusBarManager): StatusBarIOS);
diff --git a/Libraries/Components/Switch/Switch.js b/Libraries/Components/Switch/Switch.js
index 2a069baa1fb74c..3eb9f092f883d6 100644
--- a/Libraries/Components/Switch/Switch.js
+++ b/Libraries/Components/Switch/Switch.js
@@ -10,15 +10,15 @@
 
 'use strict';
 
-import SwitchNativeComponent from './SwitchNativeComponent';
 const AndroidSwitchNativeComponent = require('./AndroidSwitchNativeComponent');
 const Platform = require('../../Utilities/Platform');
 const React = require('react');
 const StyleSheet = require('../../StyleSheet/StyleSheet');
 
-import type {SyntheticEvent} from '../../Types/CoreEventTypes';
 import type {ColorValue} from '../../StyleSheet/StyleSheetTypes';
+import type {SyntheticEvent} from '../../Types/CoreEventTypes';
 import type {ViewProps} from '../View/ViewPropTypes';
+import SwitchNativeComponent from './SwitchNativeComponent';
 
 type SwitchChangeEvent = SyntheticEvent<
   $ReadOnly<{|
@@ -93,7 +93,7 @@ class Switch extends React.Component<Props> {
     typeof SwitchNativeComponent | typeof AndroidSwitchNativeComponent,
   >;
 
-  render() {
+  render(): React.Node {
     const {
       disabled,
       ios_backgroundColor,
diff --git a/Libraries/Components/TextInput/AndroidTextInputNativeComponent.js b/Libraries/Components/TextInput/AndroidTextInputNativeComponent.js
index aa6b88ea8a7a55..baf644cbb250a4 100644
--- a/Libraries/Components/TextInput/AndroidTextInputNativeComponent.js
+++ b/Libraries/Components/TextInput/AndroidTextInputNativeComponent.js
@@ -12,7 +12,7 @@
 
 import {requireNativeComponent} from 'react-native';
 
-const AndroidTextInputNativeComponent = requireNativeComponent(
+const AndroidTextInputNativeComponent: string = requireNativeComponent(
   'AndroidTextInput',
 );
 
diff --git a/Libraries/Components/TextInput/TextInputState.js b/Libraries/Components/TextInput/TextInputState.js
index 5ce5595c461892..ec5b348db7b204 100644
--- a/Libraries/Components/TextInput/TextInputState.js
+++ b/Libraries/Components/TextInput/TextInputState.js
@@ -79,7 +79,7 @@ function unregisterInput(textFieldID: number) {
   inputs.delete(textFieldID);
 }
 
-function isTextInput(textFieldID: number) {
+function isTextInput(textFieldID: number): boolean {
   return inputs.has(textFieldID);
 }
 
diff --git a/Libraries/Components/TimePickerAndroid/NativeTimePickerAndroid.js b/Libraries/Components/TimePickerAndroid/NativeTimePickerAndroid.js
index a23de52629f100..ac4aa7e6eb3e18 100644
--- a/Libraries/Components/TimePickerAndroid/NativeTimePickerAndroid.js
+++ b/Libraries/Components/TimePickerAndroid/NativeTimePickerAndroid.js
@@ -30,4 +30,4 @@ export interface Spec extends TurboModule {
   +open: (options: TimePickerOptions) => Promise<TimePickerResult>;
 }
 
-export default TurboModuleRegistry.get<Spec>('TimePickerAndroid');
+export default (TurboModuleRegistry.get<Spec>('TimePickerAndroid'): ?Spec);
diff --git a/Libraries/Components/ToastAndroid/NativeToastAndroid.js b/Libraries/Components/ToastAndroid/NativeToastAndroid.js
index 079a7d0112bcfd..f61d11bbc034e5 100644
--- a/Libraries/Components/ToastAndroid/NativeToastAndroid.js
+++ b/Libraries/Components/ToastAndroid/NativeToastAndroid.js
@@ -36,4 +36,4 @@ export interface Spec extends TurboModule {
   ) => void;
 }
 
-export default TurboModuleRegistry.getEnforcing<Spec>('ToastAndroid');
+export default (TurboModuleRegistry.getEnforcing<Spec>('ToastAndroid'): Spec);
diff --git a/Libraries/Components/Touchable/Touchable.js b/Libraries/Components/Touchable/Touchable.js
index 0170576855d5c0..a37a4fa24d4f78 100644
--- a/Libraries/Components/Touchable/Touchable.js
+++ b/Libraries/Components/Touchable/Touchable.js
@@ -23,8 +23,8 @@ const View = require('../View/View');
 const keyMirror = require('fbjs/lib/keyMirror');
 const normalizeColor = require('../../Color/normalizeColor');
 
-import type {PressEvent} from '../../Types/CoreEventTypes';
 import type {EdgeInsetsProp} from '../../StyleSheet/EdgeInsetsPropType';
+import type {PressEvent} from '../../Types/CoreEventTypes';
 
 const extractSingleTouch = nativeEvent => {
   const touches = nativeEvent.touches;
@@ -409,7 +409,9 @@ const TouchableMixin = {
    * @return {object} State object to be placed inside of
    * `this.state.touchable`.
    */
-  touchableGetInitialState: function() {
+  touchableGetInitialState: function(): $TEMPORARY$object<{|
+    touchable: $TEMPORARY$object<{|responderID: null, touchState: void|}>,
+  |}> {
     return {
       touchable: {touchState: undefined, responderID: null},
     };
@@ -419,21 +421,21 @@ const TouchableMixin = {
   /**
    * Must return true if embedded in a native platform scroll view.
    */
-  touchableHandleResponderTerminationRequest: function() {
+  touchableHandleResponderTerminationRequest: function(): any {
     return !this.props.rejectResponderTermination;
   },
 
   /**
    * Must return true to start the process of `Touchable`.
    */
-  touchableHandleStartShouldSetResponder: function() {
+  touchableHandleStartShouldSetResponder: function(): any {
     return !this.props.disabled;
   },
 
   /**
    * Return true to cancel press on long press.
    */
-  touchableLongPressCancelsPress: function() {
+  touchableLongPressCancelsPress: function(): boolean {
     return true;
   },
 
@@ -784,7 +786,7 @@ const TouchableMixin = {
     this.longPressDelayTimeout = null;
   },
 
-  _isHighlight: function(state: State) {
+  _isHighlight: function(state: State): boolean {
     return (
       state === States.RESPONDER_ACTIVE_PRESS_IN ||
       state === States.RESPONDER_ACTIVE_LONG_PRESS_IN
@@ -805,7 +807,7 @@ const TouchableMixin = {
     aY: number,
     bX: number,
     bY: number,
-  ) {
+  ): number {
     const deltaX = aX - bX;
     const deltaY = aY - bY;
     return Math.sqrt(deltaX * deltaX + deltaY * deltaY);
@@ -907,7 +909,7 @@ const TouchableMixin = {
     }
   },
 
-  withoutDefaultFocusAndBlur: {},
+  withoutDefaultFocusAndBlur: ({}: $TEMPORARY$object<{||}>),
 };
 
 /**
@@ -935,7 +937,7 @@ const Touchable = {
   }: {
     color: string | number,
     hitSlop: EdgeInsetsProp,
-  }) => {
+  }): null | React.Node => {
     if (!Touchable.TOUCH_TARGET_DEBUG) {
       return null;
     }
diff --git a/Libraries/Components/UnimplementedViews/UnimplementedView.js b/Libraries/Components/UnimplementedViews/UnimplementedView.js
index d507629710e16c..4d091bd660fe91 100644
--- a/Libraries/Components/UnimplementedViews/UnimplementedView.js
+++ b/Libraries/Components/UnimplementedViews/UnimplementedView.js
@@ -23,7 +23,7 @@ class UnimplementedView extends React.Component<$FlowFixMeProps> {
     // See ensureComponentIsNative.js for more info
   }
 
-  render() {
+  render(): React.Node {
     // Workaround require cycle from requireNativeComponent
     const View = require('../View/View');
     return (
diff --git a/Libraries/Components/View/ReactNativeViewViewConfig.js b/Libraries/Components/View/ReactNativeViewViewConfig.js
index 62b480c7f2d806..39a603a6eb7807 100644
--- a/Libraries/Components/View/ReactNativeViewViewConfig.js
+++ b/Libraries/Components/View/ReactNativeViewViewConfig.js
@@ -15,8 +15,8 @@ const ReactNativeViewConfig = {
   uiViewClassName: 'RCTView',
   baseModuleName: null,
   Manager: 'ViewManager',
-  Commands: {},
-  Constants: {},
+  Commands: ({}: $TEMPORARY$object<{||}>),
+  Constants: ({}: $TEMPORARY$object<{||}>),
   bubblingEventTypes: {
     ...ReactNativeViewViewConfigAndroid.bubblingEventTypes,
     topBlur: {
diff --git a/Libraries/Components/View/ViewNativeComponent.js b/Libraries/Components/View/ViewNativeComponent.js
index 6d8408f48f659e..f954a2d6c2f474 100644
--- a/Libraries/Components/View/ViewNativeComponent.js
+++ b/Libraries/Components/View/ViewNativeComponent.js
@@ -10,10 +10,11 @@
 
 'use strict';
 
-const ReactNative = require('../../Renderer/shims/ReactNative');
 const Platform = require('../../Utilities/Platform');
-const registerGeneratedViewConfig = require('../../Utilities/registerGeneratedViewConfig');
+const ReactNative = require('../../Renderer/shims/ReactNative');
 const ReactNativeViewViewConfigAndroid = require('./ReactNativeViewViewConfigAndroid');
+
+const registerGeneratedViewConfig = require('../../Utilities/registerGeneratedViewConfig');
 const requireNativeComponent = require('../../ReactNative/requireNativeComponent');
 
 import type {ViewProps} from './ViewPropTypes';
@@ -23,7 +24,30 @@ export type ViewNativeComponentType = Class<
 >;
 
 let NativeViewComponent;
-let viewConfig;
+let viewConfig:
+  | $TEMPORARY$object<{||}>
+  | $TEMPORARY$object<{|
+      bubblingEventTypes?: $ReadOnly<{
+        [eventName: string]: $ReadOnly<{|
+          phasedRegistrationNames: $ReadOnly<{|
+            bubbled: string,
+            captured: string,
+          |}>,
+        |}>,
+      }>,
+      directEventTypes?: $ReadOnly<{
+        [eventName: string]: $ReadOnly<{|registrationName: string|}>,
+      }>,
+      uiViewClassName: string,
+      validAttributes?: {
+        [propName: string]:
+          | true
+          | $ReadOnly<{|
+              diff?: <T>(arg1: any, arg2: any) => boolean,
+              process?: (arg1: any) => any,
+            |}>,
+      },
+    |}>;
 
 // Only use the JS view config in DEV
 if (__DEV__) {
diff --git a/Libraries/Core/ExceptionsManager.js b/Libraries/Core/ExceptionsManager.js
index 58c7b22612f0b2..7060fdd618947d 100644
--- a/Libraries/Core/ExceptionsManager.js
+++ b/Libraries/Core/ExceptionsManager.js
@@ -13,7 +13,7 @@
 import type {ExtendedError} from './Devtools/parseErrorStack';
 
 class SyntheticError extends Error {
-  name = '';
+  name: string = '';
 }
 
 /**
diff --git a/Libraries/Core/SegmentFetcher/NativeSegmentFetcher.js b/Libraries/Core/SegmentFetcher/NativeSegmentFetcher.js
index 765b8ef0e07ef3..1e5d9b4deca8ad 100644
--- a/Libraries/Core/SegmentFetcher/NativeSegmentFetcher.js
+++ b/Libraries/Core/SegmentFetcher/NativeSegmentFetcher.js
@@ -25,4 +25,4 @@ export interface Spec extends TurboModule {
   ) => void;
 }
 
-export default TurboModuleRegistry.getEnforcing<Spec>('SegmentFetcher');
+export default (TurboModuleRegistry.getEnforcing<Spec>('SegmentFetcher'): Spec);
diff --git a/Libraries/Core/Timers/JSTimers.js b/Libraries/Core/Timers/JSTimers.js
index c13732b2ce8671..e877680f778aad 100644
--- a/Libraries/Core/Timers/JSTimers.js
+++ b/Libraries/Core/Timers/JSTimers.js
@@ -9,15 +9,14 @@
  */
 'use strict';
 
+const BatchedBridge = require('../../BatchedBridge/BatchedBridge');
 const Platform = require('../../Utilities/Platform');
 const Systrace = require('../../Performance/Systrace');
 
 const invariant = require('invariant');
-const BatchedBridge = require('../../BatchedBridge/BatchedBridge');
-
-import NativeTiming from './NativeTiming';
 
 import type {ExtendedError} from '../Devtools/parseErrorStack';
+import NativeTiming from './NativeTiming';
 
 let _performanceNow = null;
 function performanceNow() {
@@ -498,7 +497,22 @@ function setSendIdleEvents(sendIdleEvents: boolean): void {
   NativeTiming.setSendIdleEvents(sendIdleEvents);
 }
 
-let ExportedJSTimers;
+let ExportedJSTimers: $TEMPORARY$object<{|
+  callIdleCallbacks: (frameTime: number) => any | void,
+  callImmediates: () => void,
+  callTimers: (timersToCall: Array<number>) => any | void,
+  cancelAnimationFrame: (timerID: number) => void,
+  cancelIdleCallback: (timerID: number) => void,
+  clearImmediate: (timerID: number) => void,
+  clearInterval: (timerID: number) => void,
+  clearTimeout: (timerID: number) => void,
+  emitTimeDriftWarning: (warningMessage: string) => any | void,
+  requestAnimationFrame: (func: any) => any | number,
+  requestIdleCallback: (func: any, options: ?any) => any | number,
+  setImmediate: (func: any, ...args: any) => number,
+  setInterval: (func: any, duration: number, ...args: any) => number,
+  setTimeout: (func: any, duration: number, ...args: any) => number,
+|}>;
 if (!NativeTiming) {
   console.warn("Timing native module is not available, can't set timers.");
   // $FlowFixMe: we can assume timers are generally available
diff --git a/Libraries/Core/Timers/NativeTiming.js b/Libraries/Core/Timers/NativeTiming.js
index f02c71e6fca604..0070adb906e615 100644
--- a/Libraries/Core/Timers/NativeTiming.js
+++ b/Libraries/Core/Timers/NativeTiming.js
@@ -24,4 +24,4 @@ export interface Spec extends TurboModule {
   +setSendIdleEvents: (sendIdleEvents: boolean) => void;
 }
 
-export default TurboModuleRegistry.get<Spec>('Timing');
+export default (TurboModuleRegistry.get<Spec>('Timing'): ?Spec);
diff --git a/Libraries/DeprecatedPropTypes/DeprecatedEdgeInsetsPropType.js b/Libraries/DeprecatedPropTypes/DeprecatedEdgeInsetsPropType.js
index 67a016fffc8d24..f4648be20b10a3 100644
--- a/Libraries/DeprecatedPropTypes/DeprecatedEdgeInsetsPropType.js
+++ b/Libraries/DeprecatedPropTypes/DeprecatedEdgeInsetsPropType.js
@@ -12,7 +12,12 @@
 
 const PropTypes = require('prop-types');
 
-const DeprecatedEdgeInsetsPropType = PropTypes.shape({
+const DeprecatedEdgeInsetsPropType: React$PropType$Primitive<{
+  bottom?: number,
+  left?: number,
+  right?: number,
+  top?: number,
+}> = PropTypes.shape({
   top: PropTypes.number,
   left: PropTypes.number,
   bottom: PropTypes.number,
diff --git a/Libraries/DeprecatedPropTypes/DeprecatedImagePropType.js b/Libraries/DeprecatedPropTypes/DeprecatedImagePropType.js
index 49e5f1de6ed415..b2d41020de77f8 100644
--- a/Libraries/DeprecatedPropTypes/DeprecatedImagePropType.js
+++ b/Libraries/DeprecatedPropTypes/DeprecatedImagePropType.js
@@ -17,9 +17,11 @@ const DeprecatedStyleSheetPropType = require('./DeprecatedStyleSheetPropType');
 const PropTypes = require('prop-types');
 
 module.exports = {
-  style: DeprecatedStyleSheetPropType(DeprecatedImageStylePropTypes),
+  style: (DeprecatedStyleSheetPropType(
+    DeprecatedImageStylePropTypes,
+  ): ReactPropsCheckType),
   source: DeprecatedImageSourcePropType,
-  defaultSource: PropTypes.oneOfType([
+  defaultSource: (PropTypes.oneOfType([
     PropTypes.shape({
       uri: PropTypes.string,
       width: PropTypes.number,
@@ -27,7 +29,9 @@ module.exports = {
       scale: PropTypes.number,
     }),
     PropTypes.number,
-  ]),
+  ]): React$PropType$Primitive<
+    {height?: number, scale?: number, uri?: string, width?: number} | number,
+  >),
 
   accessible: PropTypes.bool,
 
@@ -37,15 +41,21 @@ module.exports = {
 
   capInsets: DeprecatedEdgeInsetsPropType,
 
-  resizeMethod: PropTypes.oneOf(['auto', 'resize', 'scale']),
+  resizeMethod: (PropTypes.oneOf([
+    'auto',
+    'resize',
+    'scale',
+  ]): React$PropType$Primitive<'auto' | 'resize' | 'scale'>),
 
-  resizeMode: PropTypes.oneOf([
+  resizeMode: (PropTypes.oneOf([
     'cover',
     'contain',
     'stretch',
     'repeat',
     'center',
-  ]),
+  ]): React$PropType$Primitive<
+    'cover' | 'contain' | 'stretch' | 'repeat' | 'center',
+  >),
 
   testID: PropTypes.string,
 
diff --git a/Libraries/DeprecatedPropTypes/DeprecatedImageStylePropTypes.js b/Libraries/DeprecatedPropTypes/DeprecatedImageStylePropTypes.js
index eab9d6e49c892b..351542d9bfc7b8 100644
--- a/Libraries/DeprecatedPropTypes/DeprecatedImageStylePropTypes.js
+++ b/Libraries/DeprecatedPropTypes/DeprecatedImageStylePropTypes.js
@@ -11,27 +11,35 @@
 
 const DeprecatedColorPropType = require('./DeprecatedColorPropType');
 const DeprecatedLayoutPropTypes = require('./DeprecatedLayoutPropTypes');
-const ReactPropTypes = require('prop-types');
 const DeprecatedShadowPropTypesIOS = require('./DeprecatedShadowPropTypesIOS');
 const DeprecatedTransformPropTypes = require('./DeprecatedTransformPropTypes');
+const ReactPropTypes = require('prop-types');
 
 const ImageStylePropTypes = {
   ...DeprecatedLayoutPropTypes,
   ...DeprecatedShadowPropTypesIOS,
   ...DeprecatedTransformPropTypes,
-  resizeMode: ReactPropTypes.oneOf([
+  resizeMode: (ReactPropTypes.oneOf([
     'center',
     'contain',
     'cover',
     'repeat',
     'stretch',
-  ]),
-  backfaceVisibility: ReactPropTypes.oneOf(['visible', 'hidden']),
+  ]): React$PropType$Primitive<
+    'center' | 'contain' | 'cover' | 'repeat' | 'stretch',
+  >),
+  backfaceVisibility: (ReactPropTypes.oneOf([
+    'visible',
+    'hidden',
+  ]): React$PropType$Primitive<'visible' | 'hidden'>),
   backgroundColor: DeprecatedColorPropType,
   borderColor: DeprecatedColorPropType,
   borderWidth: ReactPropTypes.number,
   borderRadius: ReactPropTypes.number,
-  overflow: ReactPropTypes.oneOf(['visible', 'hidden']),
+  overflow: (ReactPropTypes.oneOf([
+    'visible',
+    'hidden',
+  ]): React$PropType$Primitive<'visible' | 'hidden'>),
 
   /**
    * Changes the color of all the non-transparent pixels to the tintColor.
diff --git a/Libraries/DeprecatedPropTypes/DeprecatedLayoutPropTypes.js b/Libraries/DeprecatedPropTypes/DeprecatedLayoutPropTypes.js
index 0ebccaa8d07083..4d4488a9171f1a 100644
--- a/Libraries/DeprecatedPropTypes/DeprecatedLayoutPropTypes.js
+++ b/Libraries/DeprecatedPropTypes/DeprecatedLayoutPropTypes.js
@@ -13,121 +13,129 @@
 const ReactPropTypes = require('prop-types');
 
 const LayoutPropTypes = {
-  display: ReactPropTypes.oneOf(['none', 'flex']),
-  width: ReactPropTypes.oneOfType([
+  display: (ReactPropTypes.oneOf(['none', 'flex']): React$PropType$Primitive<
+    'none' | 'flex',
+  >),
+  width: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
-  height: ReactPropTypes.oneOfType([
+  ]): React$PropType$Primitive<number | string>),
+  height: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
-  start: ReactPropTypes.oneOfType([
+  ]): React$PropType$Primitive<number | string>),
+  start: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
-  end: ReactPropTypes.oneOfType([ReactPropTypes.number, ReactPropTypes.string]),
-  top: ReactPropTypes.oneOfType([ReactPropTypes.number, ReactPropTypes.string]),
-  left: ReactPropTypes.oneOfType([
+  ]): React$PropType$Primitive<number | string>),
+  end: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
-  right: ReactPropTypes.oneOfType([
+  ]): React$PropType$Primitive<number | string>),
+  top: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
-  bottom: ReactPropTypes.oneOfType([
+  ]): React$PropType$Primitive<number | string>),
+  left: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
-  minWidth: ReactPropTypes.oneOfType([
+  ]): React$PropType$Primitive<number | string>),
+  right: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
-  maxWidth: ReactPropTypes.oneOfType([
+  ]): React$PropType$Primitive<number | string>),
+  bottom: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
-  minHeight: ReactPropTypes.oneOfType([
+  ]): React$PropType$Primitive<number | string>),
+  minWidth: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
-  maxHeight: ReactPropTypes.oneOfType([
+  ]): React$PropType$Primitive<number | string>),
+  maxWidth: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
-  margin: ReactPropTypes.oneOfType([
+  ]): React$PropType$Primitive<number | string>),
+  minHeight: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
-  marginVertical: ReactPropTypes.oneOfType([
+  ]): React$PropType$Primitive<number | string>),
+  maxHeight: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
-  marginHorizontal: ReactPropTypes.oneOfType([
+  ]): React$PropType$Primitive<number | string>),
+  margin: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
-  marginTop: ReactPropTypes.oneOfType([
+  ]): React$PropType$Primitive<number | string>),
+  marginVertical: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
-  marginBottom: ReactPropTypes.oneOfType([
+  ]): React$PropType$Primitive<number | string>),
+  marginHorizontal: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
-  marginLeft: ReactPropTypes.oneOfType([
+  ]): React$PropType$Primitive<number | string>),
+  marginTop: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
-  marginRight: ReactPropTypes.oneOfType([
+  ]): React$PropType$Primitive<number | string>),
+  marginBottom: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
-  marginStart: ReactPropTypes.oneOfType([
+  ]): React$PropType$Primitive<number | string>),
+  marginLeft: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
-  marginEnd: ReactPropTypes.oneOfType([
+  ]): React$PropType$Primitive<number | string>),
+  marginRight: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
-  padding: ReactPropTypes.oneOfType([
+  ]): React$PropType$Primitive<number | string>),
+  marginStart: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
-  paddingVertical: ReactPropTypes.oneOfType([
+  ]): React$PropType$Primitive<number | string>),
+  marginEnd: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
-  paddingHorizontal: ReactPropTypes.oneOfType([
+  ]): React$PropType$Primitive<number | string>),
+  padding: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
-  paddingTop: ReactPropTypes.oneOfType([
+  ]): React$PropType$Primitive<number | string>),
+  paddingVertical: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
-  paddingBottom: ReactPropTypes.oneOfType([
+  ]): React$PropType$Primitive<number | string>),
+  paddingHorizontal: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
-  paddingLeft: ReactPropTypes.oneOfType([
+  ]): React$PropType$Primitive<number | string>),
+  paddingTop: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
-  paddingRight: ReactPropTypes.oneOfType([
+  ]): React$PropType$Primitive<number | string>),
+  paddingBottom: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
-  paddingStart: ReactPropTypes.oneOfType([
+  ]): React$PropType$Primitive<number | string>),
+  paddingLeft: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
-  paddingEnd: ReactPropTypes.oneOfType([
+  ]): React$PropType$Primitive<number | string>),
+  paddingRight: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
+  ]): React$PropType$Primitive<number | string>),
+  paddingStart: (ReactPropTypes.oneOfType([
+    ReactPropTypes.number,
+    ReactPropTypes.string,
+  ]): React$PropType$Primitive<number | string>),
+  paddingEnd: (ReactPropTypes.oneOfType([
+    ReactPropTypes.number,
+    ReactPropTypes.string,
+  ]): React$PropType$Primitive<number | string>),
   borderWidth: ReactPropTypes.number,
   borderTopWidth: ReactPropTypes.number,
   borderStartWidth: ReactPropTypes.number,
@@ -135,56 +143,91 @@ const LayoutPropTypes = {
   borderRightWidth: ReactPropTypes.number,
   borderBottomWidth: ReactPropTypes.number,
   borderLeftWidth: ReactPropTypes.number,
-  position: ReactPropTypes.oneOf(['absolute', 'relative']),
-  flexDirection: ReactPropTypes.oneOf([
+  position: (ReactPropTypes.oneOf([
+    'absolute',
+    'relative',
+  ]): React$PropType$Primitive<'absolute' | 'relative'>),
+  flexDirection: (ReactPropTypes.oneOf([
     'row',
     'row-reverse',
     'column',
     'column-reverse',
-  ]),
-  flexWrap: ReactPropTypes.oneOf(['wrap', 'nowrap', 'wrap-reverse']),
-  justifyContent: ReactPropTypes.oneOf([
+  ]): React$PropType$Primitive<
+    'row' | 'row-reverse' | 'column' | 'column-reverse',
+  >),
+  flexWrap: (ReactPropTypes.oneOf([
+    'wrap',
+    'nowrap',
+    'wrap-reverse',
+  ]): React$PropType$Primitive<'wrap' | 'nowrap' | 'wrap-reverse'>),
+  justifyContent: (ReactPropTypes.oneOf([
     'flex-start',
     'flex-end',
     'center',
     'space-between',
     'space-around',
     'space-evenly',
-  ]),
-  alignItems: ReactPropTypes.oneOf([
+  ]): React$PropType$Primitive<
+    | 'flex-start'
+    | 'flex-end'
+    | 'center'
+    | 'space-between'
+    | 'space-around'
+    | 'space-evenly',
+  >),
+  alignItems: (ReactPropTypes.oneOf([
     'flex-start',
     'flex-end',
     'center',
     'stretch',
     'baseline',
-  ]),
-  alignSelf: ReactPropTypes.oneOf([
+  ]): React$PropType$Primitive<
+    'flex-start' | 'flex-end' | 'center' | 'stretch' | 'baseline',
+  >),
+  alignSelf: (ReactPropTypes.oneOf([
     'auto',
     'flex-start',
     'flex-end',
     'center',
     'stretch',
     'baseline',
-  ]),
-  alignContent: ReactPropTypes.oneOf([
+  ]): React$PropType$Primitive<
+    'auto' | 'flex-start' | 'flex-end' | 'center' | 'stretch' | 'baseline',
+  >),
+  alignContent: (ReactPropTypes.oneOf([
     'flex-start',
     'flex-end',
     'center',
     'stretch',
     'space-between',
     'space-around',
-  ]),
-  overflow: ReactPropTypes.oneOf(['visible', 'hidden', 'scroll']),
+  ]): React$PropType$Primitive<
+    | 'flex-start'
+    | 'flex-end'
+    | 'center'
+    | 'stretch'
+    | 'space-between'
+    | 'space-around',
+  >),
+  overflow: (ReactPropTypes.oneOf([
+    'visible',
+    'hidden',
+    'scroll',
+  ]): React$PropType$Primitive<'visible' | 'hidden' | 'scroll'>),
   flex: ReactPropTypes.number,
   flexGrow: ReactPropTypes.number,
   flexShrink: ReactPropTypes.number,
-  flexBasis: ReactPropTypes.oneOfType([
+  flexBasis: (ReactPropTypes.oneOfType([
     ReactPropTypes.number,
     ReactPropTypes.string,
-  ]),
+  ]): React$PropType$Primitive<number | string>),
   aspectRatio: ReactPropTypes.number,
   zIndex: ReactPropTypes.number,
-  direction: ReactPropTypes.oneOf(['inherit', 'ltr', 'rtl']),
+  direction: (ReactPropTypes.oneOf([
+    'inherit',
+    'ltr',
+    'rtl',
+  ]): React$PropType$Primitive<'inherit' | 'ltr' | 'rtl'>),
 };
 
 module.exports = LayoutPropTypes;
diff --git a/Libraries/DeprecatedPropTypes/DeprecatedPointPropType.js b/Libraries/DeprecatedPropTypes/DeprecatedPointPropType.js
index 9ae8c8f9872d5c..1d13e7ed74a5b9 100644
--- a/Libraries/DeprecatedPropTypes/DeprecatedPointPropType.js
+++ b/Libraries/DeprecatedPropTypes/DeprecatedPointPropType.js
@@ -12,7 +12,10 @@
 
 const PropTypes = require('prop-types');
 
-const PointPropType = PropTypes.shape({
+const PointPropType: React$PropType$Primitive<{
+  x?: number,
+  y?: number,
+}> = PropTypes.shape({
   x: PropTypes.number,
   y: PropTypes.number,
 });
diff --git a/Libraries/DeprecatedPropTypes/DeprecatedShadowPropTypesIOS.js b/Libraries/DeprecatedPropTypes/DeprecatedShadowPropTypesIOS.js
index f2d73c9578f935..3d0fe41604733e 100644
--- a/Libraries/DeprecatedPropTypes/DeprecatedShadowPropTypesIOS.js
+++ b/Libraries/DeprecatedPropTypes/DeprecatedShadowPropTypesIOS.js
@@ -14,10 +14,10 @@ const ReactPropTypes = require('prop-types');
 
 const DeprecatedShadowPropTypesIOS = {
   shadowColor: DeprecatedColorPropType,
-  shadowOffset: ReactPropTypes.shape({
+  shadowOffset: (ReactPropTypes.shape({
     width: ReactPropTypes.number,
     height: ReactPropTypes.number,
-  }),
+  }): React$PropType$Primitive<{height?: number, width?: number}>),
   shadowOpacity: ReactPropTypes.number,
   shadowRadius: ReactPropTypes.number,
 };
diff --git a/Libraries/DeprecatedPropTypes/DeprecatedTextPropTypes.js b/Libraries/DeprecatedPropTypes/DeprecatedTextPropTypes.js
index 06abb2fc3fd790..7474f53b6fb50c 100644
--- a/Libraries/DeprecatedPropTypes/DeprecatedTextPropTypes.js
+++ b/Libraries/DeprecatedPropTypes/DeprecatedTextPropTypes.js
@@ -16,12 +16,23 @@ const DeprecatedStyleSheetPropType = require('./DeprecatedStyleSheetPropType');
 const PropTypes = require('prop-types');
 const TextStylePropTypes = require('../Text/TextStylePropTypes');
 
-const stylePropType = DeprecatedStyleSheetPropType(TextStylePropTypes);
+const stylePropType: ReactPropsCheckType = DeprecatedStyleSheetPropType(
+  TextStylePropTypes,
+);
 
 module.exports = {
-  ellipsizeMode: PropTypes.oneOf(['head', 'middle', 'tail', 'clip']),
+  ellipsizeMode: (PropTypes.oneOf([
+    'head',
+    'middle',
+    'tail',
+    'clip',
+  ]): React$PropType$Primitive<'head' | 'middle' | 'tail' | 'clip'>),
   numberOfLines: PropTypes.number,
-  textBreakStrategy: PropTypes.oneOf(['simple', 'highQuality', 'balanced']),
+  textBreakStrategy: (PropTypes.oneOf([
+    'simple',
+    'highQuality',
+    'balanced',
+  ]): React$PropType$Primitive<'simple' | 'highQuality' | 'balanced'>),
   onLayout: PropTypes.func,
   onPress: PropTypes.func,
   onLongPress: PropTypes.func,
diff --git a/Libraries/DeprecatedPropTypes/DeprecatedTransformPropTypes.js b/Libraries/DeprecatedPropTypes/DeprecatedTransformPropTypes.js
index d4a408f7e9546c..78b445e754b362 100644
--- a/Libraries/DeprecatedPropTypes/DeprecatedTransformPropTypes.js
+++ b/Libraries/DeprecatedPropTypes/DeprecatedTransformPropTypes.js
@@ -41,7 +41,7 @@ const DecomposedMatrixPropType = function(
 };
 
 const DeprecatedTransformPropTypes = {
-  transform: ReactPropTypes.arrayOf(
+  transform: (ReactPropTypes.arrayOf(
     ReactPropTypes.oneOfType([
       ReactPropTypes.shape({perspective: ReactPropTypes.number}),
       ReactPropTypes.shape({rotate: ReactPropTypes.string}),
@@ -56,29 +56,44 @@ const DeprecatedTransformPropTypes = {
       ReactPropTypes.shape({skewX: ReactPropTypes.string}),
       ReactPropTypes.shape({skewY: ReactPropTypes.string}),
     ]),
-  ),
+  ): React$PropType$Primitive<
+    Array<
+      | {perspective?: number}
+      | {rotate?: string}
+      | {rotateX?: string}
+      | {rotateY?: string}
+      | {rotateZ?: string}
+      | {scale?: number}
+      | {scaleX?: number}
+      | {scaleY?: number}
+      | {translateX?: number}
+      | {translateY?: number}
+      | {skewX?: string}
+      | {skewY?: string},
+    >,
+  >),
   transformMatrix: TransformMatrixPropType,
   decomposedMatrix: DecomposedMatrixPropType,
-  scaleX: deprecatedPropType(
+  scaleX: (deprecatedPropType(
     ReactPropTypes.number,
     'Use the transform prop instead.',
-  ),
-  scaleY: deprecatedPropType(
+  ): ReactPropsCheckType),
+  scaleY: (deprecatedPropType(
     ReactPropTypes.number,
     'Use the transform prop instead.',
-  ),
-  rotation: deprecatedPropType(
+  ): ReactPropsCheckType),
+  rotation: (deprecatedPropType(
     ReactPropTypes.number,
     'Use the transform prop instead.',
-  ),
-  translateX: deprecatedPropType(
+  ): ReactPropsCheckType),
+  translateX: (deprecatedPropType(
     ReactPropTypes.number,
     'Use the transform prop instead.',
-  ),
-  translateY: deprecatedPropType(
+  ): ReactPropsCheckType),
+  translateY: (deprecatedPropType(
     ReactPropTypes.number,
     'Use the transform prop instead.',
-  ),
+  ): ReactPropsCheckType),
 };
 
 module.exports = DeprecatedTransformPropTypes;
diff --git a/Libraries/DeprecatedPropTypes/DeprecatedViewPropTypes.js b/Libraries/DeprecatedPropTypes/DeprecatedViewPropTypes.js
index 343513b5cf3570..03fd9a7c1a7691 100644
--- a/Libraries/DeprecatedPropTypes/DeprecatedViewPropTypes.js
+++ b/Libraries/DeprecatedPropTypes/DeprecatedViewPropTypes.js
@@ -11,17 +11,17 @@
 'use strict';
 
 const DeprecatedEdgeInsetsPropType = require('./DeprecatedEdgeInsetsPropType');
-const PlatformViewPropTypes = require('../Components/View/PlatformViewPropTypes');
-const PropTypes = require('prop-types');
 const DeprecatedStyleSheetPropType = require('./DeprecatedStyleSheetPropType');
 const DeprecatedViewStylePropTypes = require('./DeprecatedViewStylePropTypes');
+const PlatformViewPropTypes = require('../Components/View/PlatformViewPropTypes');
+const PropTypes = require('prop-types');
 
 const {
   DeprecatedAccessibilityRoles,
   DeprecatedAccessibilityStates,
 } = require('./DeprecatedViewAccessibility');
 
-const stylePropType = DeprecatedStyleSheetPropType(
+const stylePropType: ReactPropsCheckType = DeprecatedStyleSheetPropType(
   DeprecatedViewStylePropTypes,
 );
 
@@ -58,7 +58,9 @@ module.exports = {
    *
    * @platform ios
    */
-  accessibilityActions: PropTypes.arrayOf(PropTypes.string),
+  accessibilityActions: (PropTypes.arrayOf(
+    PropTypes.string,
+  ): React$PropType$Primitive<Array<string>>),
 
   /**
    * Prevents view from being inverted if set to true and color inversion is turned on.
@@ -70,14 +72,55 @@ module.exports = {
   /**
    * Indicates to accessibility services to treat UI component like a specific role.
    */
-  accessibilityRole: PropTypes.oneOf(DeprecatedAccessibilityRoles),
+  accessibilityRole: (PropTypes.oneOf(
+    DeprecatedAccessibilityRoles,
+  ): React$PropType$Primitive<
+    | 'none'
+    | 'button'
+    | 'link'
+    | 'search'
+    | 'image'
+    | 'keyboardkey'
+    | 'text'
+    | 'adjustable'
+    | 'imagebutton'
+    | 'header'
+    | 'summary'
+    | 'alert'
+    | 'checkbox'
+    | 'combobox'
+    | 'menu'
+    | 'menubar'
+    | 'menuitem'
+    | 'progressbar'
+    | 'radio'
+    | 'radiogroup'
+    | 'scrollbar'
+    | 'spinbutton'
+    | 'switch'
+    | 'tab'
+    | 'tablist'
+    | 'timer'
+    | 'toolbar',
+  >),
 
   /**
    * Indicates to accessibility services that UI Component is in a specific State.
    */
-  accessibilityStates: PropTypes.arrayOf(
+  accessibilityStates: (PropTypes.arrayOf(
     PropTypes.oneOf(DeprecatedAccessibilityStates),
-  ),
+  ): React$PropType$Primitive<
+    Array<
+      | 'selected'
+      | 'disabled'
+      | 'checked'
+      | 'unchecked'
+      | 'busy'
+      | 'expanded'
+      | 'collapsed'
+      | 'hasPopup',
+    >,
+  >),
   accessibilityState: PropTypes.object,
   /**
    * Indicates to accessibility services whether the user should be notified
@@ -87,7 +130,11 @@ module.exports = {
    *
    * See http://facebook.github.io/react-native/docs/view.html#accessibilityliveregion
    */
-  accessibilityLiveRegion: PropTypes.oneOf(['none', 'polite', 'assertive']),
+  accessibilityLiveRegion: (PropTypes.oneOf([
+    'none',
+    'polite',
+    'assertive',
+  ]): React$PropType$Primitive<'none' | 'polite' | 'assertive'>),
 
   /**
    * Controls how view is important for accessibility which is if it
@@ -98,12 +145,12 @@ module.exports = {
    *
    * See http://facebook.github.io/react-native/docs/view.html#importantforaccessibility
    */
-  importantForAccessibility: PropTypes.oneOf([
+  importantForAccessibility: (PropTypes.oneOf([
     'auto',
     'yes',
     'no',
     'no-hide-descendants',
-  ]),
+  ]): React$PropType$Primitive<'auto' | 'yes' | 'no' | 'no-hide-descendants'>),
 
   /**
    * A value indicating whether VoiceOver should ignore the elements
@@ -314,7 +361,12 @@ module.exports = {
    *
    * See http://facebook.github.io/react-native/docs/view.html#pointerevents
    */
-  pointerEvents: PropTypes.oneOf(['box-none', 'none', 'box-only', 'auto']),
+  pointerEvents: (PropTypes.oneOf([
+    'box-none',
+    'none',
+    'box-only',
+    'auto',
+  ]): React$PropType$Primitive<'box-none' | 'none' | 'box-only' | 'auto'>),
 
   /**
    * See http://facebook.github.io/react-native/docs/style.html
diff --git a/Libraries/DeprecatedPropTypes/DeprecatedViewStylePropTypes.js b/Libraries/DeprecatedPropTypes/DeprecatedViewStylePropTypes.js
index 373174edd1eaf2..8b7036bd60761d 100644
--- a/Libraries/DeprecatedPropTypes/DeprecatedViewStylePropTypes.js
+++ b/Libraries/DeprecatedPropTypes/DeprecatedViewStylePropTypes.js
@@ -12,9 +12,9 @@
 
 const DeprecatedColorPropType = require('./DeprecatedColorPropType');
 const DeprecatedLayoutPropTypes = require('./DeprecatedLayoutPropTypes');
-const ReactPropTypes = require('prop-types');
 const DeprecatedShadowPropTypesIOS = require('./DeprecatedShadowPropTypesIOS');
 const DeprecatedTransformPropTypes = require('./DeprecatedTransformPropTypes');
+const ReactPropTypes = require('prop-types');
 
 /**
  * Warning: Some of these properties may not be supported in all releases.
@@ -23,7 +23,10 @@ const DeprecatedViewStylePropTypes = {
   ...DeprecatedLayoutPropTypes,
   ...DeprecatedShadowPropTypesIOS,
   ...DeprecatedTransformPropTypes,
-  backfaceVisibility: ReactPropTypes.oneOf(['visible', 'hidden']),
+  backfaceVisibility: (ReactPropTypes.oneOf([
+    'visible',
+    'hidden',
+  ]): React$PropType$Primitive<'visible' | 'hidden'>),
   backgroundColor: DeprecatedColorPropType,
   borderColor: DeprecatedColorPropType,
   borderTopColor: DeprecatedColorPropType,
@@ -41,7 +44,11 @@ const DeprecatedViewStylePropTypes = {
   borderBottomRightRadius: ReactPropTypes.number,
   borderBottomStartRadius: ReactPropTypes.number,
   borderBottomEndRadius: ReactPropTypes.number,
-  borderStyle: ReactPropTypes.oneOf(['solid', 'dotted', 'dashed']),
+  borderStyle: (ReactPropTypes.oneOf([
+    'solid',
+    'dotted',
+    'dashed',
+  ]): React$PropType$Primitive<'solid' | 'dotted' | 'dashed'>),
   borderWidth: ReactPropTypes.number,
   borderTopWidth: ReactPropTypes.number,
   borderRightWidth: ReactPropTypes.number,
diff --git a/Libraries/EventEmitter/RCTDeviceEventEmitter.js b/Libraries/EventEmitter/RCTDeviceEventEmitter.js
index f3192d0bb4f01b..0b4c15d501d6b8 100644
--- a/Libraries/EventEmitter/RCTDeviceEventEmitter.js
+++ b/Libraries/EventEmitter/RCTDeviceEventEmitter.js
@@ -81,4 +81,4 @@ class RCTDeviceEventEmitter extends EventEmitter {
   }
 }
 
-module.exports = new RCTDeviceEventEmitter();
+module.exports = (new RCTDeviceEventEmitter(): RCTDeviceEventEmitter);
diff --git a/Libraries/Experimental/Incremental.js b/Libraries/Experimental/Incremental.js
index e7f3e82c2126e6..8ccb315d6a8dc0 100644
--- a/Libraries/Experimental/Incremental.js
+++ b/Libraries/Experimental/Incremental.js
@@ -11,9 +11,8 @@
 'use strict';
 
 const InteractionManager = require('../Interaction/InteractionManager');
-const React = require('react');
-
 const PropTypes = require('prop-types');
+const React = require('react');
 
 const infoLog = require('../Utilities/infoLog');
 
@@ -104,11 +103,16 @@ class Incremental extends React.Component<Props, State> {
   _mounted: boolean;
   _rendered: boolean;
 
-  static defaultProps = {
+  static defaultProps: $TEMPORARY$object<{|name: string|}> = {
     name: '',
   };
 
-  static contextTypes = {
+  static contextTypes:
+    | any
+    | $TEMPORARY$object<{|
+        incrementalGroup: React$PropType$Primitive<any>,
+        incrementalGroupEnabled: React$PropType$Primitive<boolean>,
+      |}> = {
     incrementalGroup: PropTypes.object,
     incrementalGroupEnabled: PropTypes.bool,
   };
diff --git a/Libraries/Experimental/IncrementalExample.js b/Libraries/Experimental/IncrementalExample.js
index 906bb281bcd110..4d551053e4f193 100644
--- a/Libraries/Experimental/IncrementalExample.js
+++ b/Libraries/Experimental/IncrementalExample.js
@@ -93,8 +93,9 @@ function Block(props: Object) {
 const Row = (props: Object) => <View style={styles.row} {...props} />;
 
 class IncrementalExample extends React.Component<mixed, {stats: ?Object}> {
-  static title = '<Incremental*>';
-  static description = 'Enables incremental rendering of complex components.';
+  static title: string = '<Incremental*>';
+  static description: string =
+    'Enables incremental rendering of complex components.';
   start: number;
   constructor(props: mixed, context: mixed) {
     super(props, context);
diff --git a/Libraries/Experimental/IncrementalPresenter.js b/Libraries/Experimental/IncrementalPresenter.js
index a3f8069c93ca74..561da9bbd83f17 100644
--- a/Libraries/Experimental/IncrementalPresenter.js
+++ b/Libraries/Experimental/IncrementalPresenter.js
@@ -15,9 +15,9 @@ const PropTypes = require('prop-types');
 const React = require('react');
 const View = require('../Components/View/View');
 
-import type {Context} from './Incremental';
 import type {ViewStyleProp} from '../StyleSheet/StyleSheet';
 import type {LayoutEvent} from '../Types/CoreEventTypes';
+import type {Context} from './Incremental';
 
 /**
  * WARNING: EXPERIMENTAL. Breaking changes will probably happen a lot and will
@@ -44,7 +44,12 @@ class IncrementalPresenter extends React.Component<Props> {
   context: Context;
   _isDone: boolean;
 
-  static contextTypes = {
+  static contextTypes:
+    | any
+    | $TEMPORARY$object<{|
+        incrementalGroup: React$PropType$Primitive<any>,
+        incrementalGroupEnabled: React$PropType$Primitive<boolean>,
+      |}> = {
     incrementalGroup: PropTypes.object,
     incrementalGroupEnabled: PropTypes.bool,
   };
@@ -67,7 +72,7 @@ class IncrementalPresenter extends React.Component<Props> {
     }
     this.props.onDone && this.props.onDone();
   }
-  render() {
+  render(): React.Node {
     let style: ViewStyleProp;
     if (
       this.props.disabled !== true &&
diff --git a/Libraries/Experimental/WindowedListView.js b/Libraries/Experimental/WindowedListView.js
index 5684752ac5b85f..05c2fa038f08b0 100644
--- a/Libraries/Experimental/WindowedListView.js
+++ b/Libraries/Experimental/WindowedListView.js
@@ -170,7 +170,15 @@ class WindowedListView extends React.Component<Props, State> {
   _scrollRef: ?ScrollView;
   _viewabilityHelper: ViewabilityHelper;
 
-  static defaultProps = {
+  static defaultProps: $TEMPORARY$object<{|
+    disableIncrementalRendering: boolean,
+    initialNumToRender: number,
+    maxNumToRender: number,
+    numToRenderAhead: number,
+    recomputeRowsBatchingPeriod: number,
+    renderScrollComponent: (props: any) => React.Node,
+    viewablePercentThreshold: number,
+  |}> = {
     initialNumToRender: 10,
     maxNumToRender: 30,
     numToRenderAhead: 10,
diff --git a/Libraries/HeapCapture/NativeHeapCapture.js b/Libraries/HeapCapture/NativeHeapCapture.js
index 95c2f7f7cff75b..7374cd357297bb 100644
--- a/Libraries/HeapCapture/NativeHeapCapture.js
+++ b/Libraries/HeapCapture/NativeHeapCapture.js
@@ -21,4 +21,4 @@ export interface Spec extends TurboModule {
   +captureComplete: (path: string, error: ?string) => void;
 }
 
-export default TurboModuleRegistry.get<Spec>('HeapCapture');
+export default (TurboModuleRegistry.get<Spec>('HeapCapture'): ?Spec);
diff --git a/Libraries/Image/Image.ios.js b/Libraries/Image/Image.ios.js
index 59411e6d6aedf8..e92ef67b336299 100644
--- a/Libraries/Image/Image.ios.js
+++ b/Libraries/Image/Image.ios.js
@@ -47,7 +47,7 @@ function getSizeWithHeaders(
   headers: {[string]: string},
   success: (width: number, height: number) => void,
   failure?: (error: any) => void,
-) {
+): any {
   return ImageViewManager.getSizeWithHeaders({uri, headers})
     .then(function(sizes) {
       success(sizes.width, sizes.height);
@@ -60,7 +60,7 @@ function getSizeWithHeaders(
     );
 }
 
-function prefetch(url: string) {
+function prefetch(url: string): any {
   return ImageViewManager.prefetchImage(url);
 }
 
diff --git a/Libraries/Image/ImageBackground.js b/Libraries/Image/ImageBackground.js
index 22d684ba90bf32..e6baa48012c608 100644
--- a/Libraries/Image/ImageBackground.js
+++ b/Libraries/Image/ImageBackground.js
@@ -56,7 +56,7 @@ class ImageBackground extends React.Component<$FlowFixMeProps> {
     this._viewRef = ref;
   };
 
-  render() {
+  render(): React.Node {
     const {children, style, imageStyle, imageRef, ...props} = this.props;
 
     return (
diff --git a/Libraries/Image/ImagePickerIOS.js b/Libraries/Image/ImagePickerIOS.js
index 378636d0fcbaa2..587d89b6ed6fe8 100644
--- a/Libraries/Image/ImagePickerIOS.js
+++ b/Libraries/Image/ImagePickerIOS.js
@@ -14,11 +14,11 @@ import NativeImagePickerIOS from './NativeImagePickerIOS';
 import invariant from 'invariant';
 
 const ImagePickerIOS = {
-  canRecordVideos: function(callback: (result: boolean) => void) {
+  canRecordVideos: function(callback: (result: boolean) => void): void {
     invariant(NativeImagePickerIOS, 'ImagePickerIOS is not available');
     return NativeImagePickerIOS.canRecordVideos(callback);
   },
-  canUseCamera: function(callback: (result: boolean) => void) {
+  canUseCamera: function(callback: (result: boolean) => void): void {
     invariant(NativeImagePickerIOS, 'ImagePickerIOS is not available');
     return NativeImagePickerIOS.canUseCamera(callback);
   },
@@ -29,7 +29,7 @@ const ImagePickerIOS = {
     |}>,
     successCallback: (imageURL: string, height: number, width: number) => void,
     cancelCallback: () => void,
-  ) {
+  ): void {
     invariant(NativeImagePickerIOS, 'ImagePickerIOS is not available');
 
     var newConfig = {
@@ -58,7 +58,7 @@ const ImagePickerIOS = {
     |}>,
     successCallback: (imageURL: string, height: number, width: number) => void,
     cancelCallback: () => void,
-  ) {
+  ): void {
     invariant(NativeImagePickerIOS, 'ImagePickerIOS is not available');
 
     var newConfig = {
diff --git a/Libraries/Image/ImageViewNativeComponent.js b/Libraries/Image/ImageViewNativeComponent.js
index c0dbee693b7339..06722105bdc229 100644
--- a/Libraries/Image/ImageViewNativeComponent.js
+++ b/Libraries/Image/ImageViewNativeComponent.js
@@ -12,6 +12,6 @@
 
 const requireNativeComponent = require('../ReactNative/requireNativeComponent');
 
-const ImageViewNativeComponent = requireNativeComponent('RCTImageView');
+const ImageViewNativeComponent: string = requireNativeComponent('RCTImageView');
 
 module.exports = ImageViewNativeComponent;
diff --git a/Libraries/Image/NativeImagePickerIOS.js b/Libraries/Image/NativeImagePickerIOS.js
index 668a2af7e34c9a..895f95f39f69d1 100644
--- a/Libraries/Image/NativeImagePickerIOS.js
+++ b/Libraries/Image/NativeImagePickerIOS.js
@@ -35,4 +35,4 @@ export interface Spec extends TurboModule {
   ) => void;
 }
 
-export default TurboModuleRegistry.get<Spec>('ImagePickerIOS');
+export default (TurboModuleRegistry.get<Spec>('ImagePickerIOS'): ?Spec);
diff --git a/Libraries/Image/RelativeImageStub.js b/Libraries/Image/RelativeImageStub.js
index 6349a393f59064..040392a75e2e07 100644
--- a/Libraries/Image/RelativeImageStub.js
+++ b/Libraries/Image/RelativeImageStub.js
@@ -15,7 +15,7 @@
 
 const AssetRegistry = require('./AssetRegistry');
 
-module.exports = AssetRegistry.registerAsset({
+module.exports = (AssetRegistry.registerAsset({
   __packager_asset: true,
   fileSystemLocation: '/full/path/to/directory',
   httpServerLocation: '/assets/full/path/to/directory',
@@ -25,4 +25,4 @@ module.exports = AssetRegistry.registerAsset({
   hash: 'nonsense',
   name: 'icon',
   type: 'png',
-});
+}): number);
diff --git a/Libraries/Image/TextInlineImageNativeComponent.js b/Libraries/Image/TextInlineImageNativeComponent.js
index b8cb7a50f8eb59..144e4314f8d645 100644
--- a/Libraries/Image/TextInlineImageNativeComponent.js
+++ b/Libraries/Image/TextInlineImageNativeComponent.js
@@ -12,6 +12,6 @@
 
 const requireNativeComponent = require('../ReactNative/requireNativeComponent');
 
-const TextInlineImage = requireNativeComponent('RCTTextInlineImage');
+const TextInlineImage: string = requireNativeComponent('RCTTextInlineImage');
 
 module.exports = TextInlineImage;
diff --git a/Libraries/Image/assetPathUtils.js b/Libraries/Image/assetPathUtils.js
index 402680cef72779..6281c959984d9c 100644
--- a/Libraries/Image/assetPathUtils.js
+++ b/Libraries/Image/assetPathUtils.js
@@ -44,7 +44,10 @@ const drawableFileTypes = new Set([
   'xml',
 ]);
 
-function getAndroidResourceFolderName(asset: PackagerAsset, scale: number) {
+function getAndroidResourceFolderName(
+  asset: PackagerAsset,
+  scale: number,
+): string | $TEMPORARY$string<'raw'> {
   if (!drawableFileTypes.has(asset.type)) {
     return 'raw';
   }
@@ -63,7 +66,7 @@ function getAndroidResourceFolderName(asset: PackagerAsset, scale: number) {
   return androidFolder;
 }
 
-function getAndroidResourceIdentifier(asset: PackagerAsset) {
+function getAndroidResourceIdentifier(asset: PackagerAsset): string {
   var folderPath = getBasePath(asset);
   return (folderPath + '/' + asset.name)
     .toLowerCase()
@@ -72,7 +75,7 @@ function getAndroidResourceIdentifier(asset: PackagerAsset) {
     .replace(/^assets_/, ''); // Remove "assets_" prefix
 }
 
-function getBasePath(asset: PackagerAsset) {
+function getBasePath(asset: PackagerAsset): string {
   var basePath = asset.httpServerLocation;
   if (basePath[0] === '/') {
     basePath = basePath.substr(1);
diff --git a/Libraries/Inspector/BorderBox.js b/Libraries/Inspector/BorderBox.js
index 3ab66f10a0fb20..886beb784d5922 100644
--- a/Libraries/Inspector/BorderBox.js
+++ b/Libraries/Inspector/BorderBox.js
@@ -14,7 +14,7 @@ const React = require('react');
 const View = require('../Components/View/View');
 
 class BorderBox extends React.Component<$FlowFixMeProps> {
-  render() {
+  render(): $FlowFixMe | React.Node {
     const box = this.props.box;
     if (!box) {
       return this.props.children;
diff --git a/Libraries/Inspector/BoxInspector.js b/Libraries/Inspector/BoxInspector.js
index bd1f3d376f5f83..e1002f568ca0f4 100644
--- a/Libraries/Inspector/BoxInspector.js
+++ b/Libraries/Inspector/BoxInspector.js
@@ -14,6 +14,7 @@ const React = require('react');
 const StyleSheet = require('../StyleSheet/StyleSheet');
 const Text = require('../Text/Text');
 const View = require('../Components/View/View');
+
 const resolveBoxStyle = require('./resolveBoxStyle');
 
 const blank = {
@@ -24,7 +25,7 @@ const blank = {
 };
 
 class BoxInspector extends React.Component<$FlowFixMeProps> {
-  render() {
+  render(): React.Node {
     const frame = this.props.frame;
     const style = this.props.style;
     const margin = (style && resolveBoxStyle('margin', style)) || blank;
diff --git a/Libraries/Inspector/ElementBox.js b/Libraries/Inspector/ElementBox.js
index 9f6c0c4bf204ed..2e67b18f7720d8 100644
--- a/Libraries/Inspector/ElementBox.js
+++ b/Libraries/Inspector/ElementBox.js
@@ -11,16 +11,16 @@
 'use strict';
 
 const BorderBox = require('./BorderBox');
+const Dimensions = require('../Utilities/Dimensions');
 const React = require('react');
 const StyleSheet = require('../StyleSheet/StyleSheet');
 const View = require('../Components/View/View');
-const Dimensions = require('../Utilities/Dimensions');
 
 const flattenStyle = require('../StyleSheet/flattenStyle');
 const resolveBoxStyle = require('./resolveBoxStyle');
 
 class ElementBox extends React.Component<$FlowFixMeProps> {
-  render() {
+  render(): React.Node {
     const style = flattenStyle(this.props.style) || {};
     let margin = resolveBoxStyle('margin', style);
     let padding = resolveBoxStyle('padding', style);
diff --git a/Libraries/Inspector/ElementProperties.js b/Libraries/Inspector/ElementProperties.js
index 3cc8f4bfa5f1ba..31f74406a9ed11 100644
--- a/Libraries/Inspector/ElementProperties.js
+++ b/Libraries/Inspector/ElementProperties.js
@@ -38,7 +38,7 @@ type Props = $ReadOnly<{|
 |}>;
 
 class ElementProperties extends React.Component<Props> {
-  render() {
+  render(): React.Node {
     const style = flattenStyle(this.props.style);
     const selection = this.props.selection;
     let openFileButton;
diff --git a/Libraries/Inspector/Inspector.js b/Libraries/Inspector/Inspector.js
index a9ddf5919572be..22dd2655b61722 100644
--- a/Libraries/Inspector/Inspector.js
+++ b/Libraries/Inspector/Inspector.js
@@ -115,7 +115,7 @@ class Inspector extends React.Component<
     this.setState({inspectedViewTag: newProps.inspectedViewTag});
   }
 
-  attachToDevtools = (agent: Object) => {
+  attachToDevtools: (agent: any) => void = (agent: Object) => {
     let _hideWait = null;
     const hlSub = agent.sub('highlight', ({node, name, props}) => {
       clearTimeout(_hideWait);
@@ -239,7 +239,7 @@ class Inspector extends React.Component<
     });
   }
 
-  render() {
+  render(): React.Node {
     const panelContainerStyle =
       this.state.panelPos === 'bottom'
         ? {bottom: 0}
diff --git a/Libraries/Inspector/InspectorOverlay.js b/Libraries/Inspector/InspectorOverlay.js
index 540afb73c1c998..878ee5e6ca1591 100644
--- a/Libraries/Inspector/InspectorOverlay.js
+++ b/Libraries/Inspector/InspectorOverlay.js
@@ -17,8 +17,8 @@ const StyleSheet = require('../StyleSheet/StyleSheet');
 const UIManager = require('../ReactNative/UIManager');
 const View = require('../Components/View/View');
 
-import type {PressEvent} from '../Types/CoreEventTypes';
 import type {ViewStyleProp} from '../StyleSheet/StyleSheet';
+import type {PressEvent} from '../Types/CoreEventTypes';
 
 type Inspected = $ReadOnly<{|
   frame?: Object,
@@ -32,7 +32,7 @@ type Props = $ReadOnly<{|
 |}>;
 
 class InspectorOverlay extends React.Component<Props> {
-  findViewForTouchEvent = (e: PressEvent) => {
+  findViewForTouchEvent: (e: PressEvent) => void = (e: PressEvent) => {
     const {locationX, locationY} = e.nativeEvent.touches[0];
     UIManager.findSubviewIn(
       this.props.inspectedViewTag,
@@ -47,12 +47,12 @@ class InspectorOverlay extends React.Component<Props> {
     );
   };
 
-  shouldSetResponser = (e: PressEvent): boolean => {
+  shouldSetResponser: (e: PressEvent) => boolean = (e: PressEvent): boolean => {
     this.findViewForTouchEvent(e);
     return true;
   };
 
-  render() {
+  render(): React.Node {
     let content = null;
     if (this.props.inspected) {
       content = (
diff --git a/Libraries/Inspector/InspectorPanel.js b/Libraries/Inspector/InspectorPanel.js
index 8aac5987843494..9cf47a83770a0f 100644
--- a/Libraries/Inspector/InspectorPanel.js
+++ b/Libraries/Inspector/InspectorPanel.js
@@ -51,7 +51,7 @@ type Props = $ReadOnly<{|
 |}>;
 
 class InspectorPanel extends React.Component<Props> {
-  renderWaiting() {
+  renderWaiting(): React.Node {
     if (this.props.inspecting) {
       return (
         <Text style={styles.waitingText}>Tap something to inspect it</Text>
@@ -60,7 +60,7 @@ class InspectorPanel extends React.Component<Props> {
     return <Text style={styles.waitingText}>Nothing is inspected</Text>;
   }
 
-  render() {
+  render(): React.Node {
     let contents;
     if (this.props.inspected) {
       contents = (
diff --git a/Libraries/Inspector/NetworkOverlay.js b/Libraries/Inspector/NetworkOverlay.js
index a39370bcee8e65..b2956a077614ba 100644
--- a/Libraries/Inspector/NetworkOverlay.js
+++ b/Libraries/Inspector/NetworkOverlay.js
@@ -103,7 +103,7 @@ class NetworkOverlay extends React.Component<Props, State> {
   // Map of `xhr._index` -> `index in `this.state.requests`.
   _xhrIdMap: {[key: number]: number} = {};
 
-  state = {
+  state: State = {
     detailRowId: null,
     requests: [],
   };
diff --git a/Libraries/Inspector/PerformanceOverlay.js b/Libraries/Inspector/PerformanceOverlay.js
index 9d1f63c8c6a435..56b86fb16c53b9 100644
--- a/Libraries/Inspector/PerformanceOverlay.js
+++ b/Libraries/Inspector/PerformanceOverlay.js
@@ -17,7 +17,7 @@ const Text = require('../Text/Text');
 const View = require('../Components/View/View');
 
 class PerformanceOverlay extends React.Component<{}> {
-  render() {
+  render(): React.Node {
     const perfLogs = PerformanceLogger.getTimespans();
     const items = [];
 
diff --git a/Libraries/Inspector/StyleInspector.js b/Libraries/Inspector/StyleInspector.js
index 332fe22bfed35f..64f001b116d82d 100644
--- a/Libraries/Inspector/StyleInspector.js
+++ b/Libraries/Inspector/StyleInspector.js
@@ -16,7 +16,7 @@ const Text = require('../Text/Text');
 const View = require('../Components/View/View');
 
 class StyleInspector extends React.Component<$FlowFixMeProps> {
-  render() {
+  render(): React.Node {
     if (!this.props.style) {
       return <Text style={styles.noStyle}>No style</Text>;
     }
diff --git a/Libraries/Interaction/InteractionManager.js b/Libraries/Interaction/InteractionManager.js
index a8148dd63af7d1..8784d9bce5351a 100644
--- a/Libraries/Interaction/InteractionManager.js
+++ b/Libraries/Interaction/InteractionManager.js
@@ -139,7 +139,7 @@ const InteractionManager = {
     _deleteInteractionSet.add(handle);
   },
 
-  addListener: _emitter.addListener.bind(_emitter),
+  addListener: (_emitter.addListener.bind(_emitter): $FlowFixMe),
 
   /**
    * A positive number will use setTimeout to schedule any tasks after the
diff --git a/Libraries/Interaction/PanResponder.js b/Libraries/Interaction/PanResponder.js
index 2b20faebe32544..d70797df24cac3 100644
--- a/Libraries/Interaction/PanResponder.js
+++ b/Libraries/Interaction/PanResponder.js
@@ -383,7 +383,25 @@ const PanResponder = {
    *  accordingly. (numberActiveTouches) may not be totally accurate unless you
    *  are the responder.
    */
-  create(config: PanResponderConfig) {
+  create(
+    config: PanResponderConfig,
+  ): $TEMPORARY$object<{|
+    getInteractionHandle: () => ?number,
+    panHandlers: $TEMPORARY$object<{|
+      onMoveShouldSetResponder: (event: PressEvent) => boolean,
+      onMoveShouldSetResponderCapture: (event: PressEvent) => boolean,
+      onResponderEnd: (event: PressEvent) => void,
+      onResponderGrant: (event: PressEvent) => boolean,
+      onResponderMove: (event: PressEvent) => void,
+      onResponderReject: (event: PressEvent) => void,
+      onResponderRelease: (event: PressEvent) => void,
+      onResponderStart: (event: PressEvent) => void,
+      onResponderTerminate: (event: PressEvent) => void,
+      onResponderTerminationRequest: (event: PressEvent) => boolean,
+      onStartShouldSetResponder: (event: PressEvent) => boolean,
+      onStartShouldSetResponderCapture: (event: PressEvent) => boolean,
+    |}>,
+  |}> {
     const interactionState = {
       handle: (null: ?number),
     };
diff --git a/Libraries/JSInspector/NetworkAgent.js b/Libraries/JSInspector/NetworkAgent.js
index 7f9c63d63f7a4a..4ad89bae6afb36 100644
--- a/Libraries/JSInspector/NetworkAgent.js
+++ b/Libraries/JSInspector/NetworkAgent.js
@@ -251,7 +251,7 @@ type EnableArgs = {
 };
 
 class NetworkAgent extends InspectorAgent {
-  static DOMAIN = 'Network';
+  static DOMAIN: $TEMPORARY$string<'Network'> = 'Network';
 
   _sendEvent: EventSender;
   _interceptor: ?Interceptor;
diff --git a/Libraries/LayoutAnimation/LayoutAnimation.js b/Libraries/LayoutAnimation/LayoutAnimation.js
index 20018cf566b20c..4cf9b0db4c4708 100644
--- a/Libraries/LayoutAnimation/LayoutAnimation.js
+++ b/Libraries/LayoutAnimation/LayoutAnimation.js
@@ -10,9 +10,10 @@
 
 'use strict';
 
-import Platform from '../Utilities/Platform';
 const UIManager = require('../ReactNative/UIManager');
 
+import Platform from '../Utilities/Platform';
+
 type Type =
   | 'spring'
   | 'linear'
@@ -66,8 +67,12 @@ function create(
 }
 
 const Presets = {
-  easeInEaseOut: create(300, 'easeInEaseOut', 'opacity'),
-  linear: create(500, 'linear', 'opacity'),
+  easeInEaseOut: (create(
+    300,
+    'easeInEaseOut',
+    'opacity',
+  ): LayoutAnimationConfig),
+  linear: (create(500, 'linear', 'opacity'): LayoutAnimationConfig),
   spring: {
     duration: 700,
     create: {
@@ -132,9 +137,15 @@ const LayoutAnimation = {
     console.error('LayoutAnimation.checkConfig(...) has been disabled.');
   },
   Presets,
-  easeInEaseOut: configureNext.bind(null, Presets.easeInEaseOut),
-  linear: configureNext.bind(null, Presets.linear),
-  spring: configureNext.bind(null, Presets.spring),
+  easeInEaseOut: (configureNext.bind(null, Presets.easeInEaseOut): (
+    onAnimationDidEnd?: any,
+  ) => void),
+  linear: (configureNext.bind(null, Presets.linear): (
+    onAnimationDidEnd?: any,
+  ) => void),
+  spring: (configureNext.bind(null, Presets.spring): (
+    onAnimationDidEnd?: any,
+  ) => void),
 };
 
 module.exports = LayoutAnimation;
diff --git a/Libraries/Linking/Linking.js b/Libraries/Linking/Linking.js
index f15023e55325ec..284f2336a5b3d4 100644
--- a/Libraries/Linking/Linking.js
+++ b/Libraries/Linking/Linking.js
@@ -117,4 +117,4 @@ class Linking extends NativeEventEmitter {
   }
 }
 
-module.exports = new Linking();
+module.exports = (new Linking(): Linking);
diff --git a/Libraries/Linking/NativeLinking.js b/Libraries/Linking/NativeLinking.js
index f661a45184a583..cbb7c1a00bdc6f 100644
--- a/Libraries/Linking/NativeLinking.js
+++ b/Libraries/Linking/NativeLinking.js
@@ -32,6 +32,6 @@ export interface Spec extends TurboModule {
   +removeListeners: (count: number) => void;
 }
 
-export default (Platform.OS === 'android'
+export default ((Platform.OS === 'android'
   ? TurboModuleRegistry.getEnforcing<Spec>('IntentAndroid')
-  : TurboModuleRegistry.getEnforcing<Spec>('LinkingManager'));
+  : TurboModuleRegistry.getEnforcing<Spec>('LinkingManager')): Spec);
diff --git a/Libraries/Lists/__flowtests__/FlatList-flowtest.js b/Libraries/Lists/__flowtests__/FlatList-flowtest.js
index 71b5f10004cbe2..99db43079f5f70 100644
--- a/Libraries/Lists/__flowtests__/FlatList-flowtest.js
+++ b/Libraries/Lists/__flowtests__/FlatList-flowtest.js
@@ -18,7 +18,7 @@ function renderMyListItem(info: {item: {title: string}, index: number}) {
 }
 
 module.exports = {
-  testEverythingIsFine() {
+  testEverythingIsFine(): React.Node {
     const data = [
       {
         title: 'Title Text',
@@ -28,7 +28,7 @@ module.exports = {
     return <FlatList renderItem={renderMyListItem} data={data} />;
   },
 
-  testBadDataWithTypicalItem() {
+  testBadDataWithTypicalItem(): React.Node {
     const data = [
       {
         // $FlowExpectedError - bad title type 6, should be string
@@ -39,7 +39,7 @@ module.exports = {
     return <FlatList renderItem={renderMyListItem} data={data} />;
   },
 
-  testMissingFieldWithTypicalItem() {
+  testMissingFieldWithTypicalItem(): React.Node {
     const data = [
       {
         key: 1,
@@ -49,7 +49,7 @@ module.exports = {
     return <FlatList renderItem={renderMyListItem} data={data} />;
   },
 
-  testGoodDataWithBadCustomRenderItemFunction() {
+  testGoodDataWithBadCustomRenderItemFunction(): React.Node {
     const data = [
       {
         widget: 6,
@@ -71,7 +71,7 @@ module.exports = {
     );
   },
 
-  testBadRenderItemFunction() {
+  testBadRenderItemFunction(): $TEMPORARY$array<React.Node> {
     const data = [
       {
         title: 'foo',
@@ -99,7 +99,7 @@ module.exports = {
     ];
   },
 
-  testOtherBadProps() {
+  testOtherBadProps(): $TEMPORARY$array<React.Node> {
     return [
       // $FlowExpectedError - bad numColumns type "lots"
       <FlatList renderItem={renderMyListItem} data={[]} numColumns="lots" />,
diff --git a/Libraries/Lists/__flowtests__/SectionList-flowtest.js b/Libraries/Lists/__flowtests__/SectionList-flowtest.js
index 9f70f43551fed1..44d8d008b7ba03 100644
--- a/Libraries/Lists/__flowtests__/SectionList-flowtest.js
+++ b/Libraries/Lists/__flowtests__/SectionList-flowtest.js
@@ -22,7 +22,7 @@ const renderMyHeader = ({section}: {section: {fooNumber: number} & Object}) => (
 );
 
 module.exports = {
-  testGoodDataWithGoodItem() {
+  testGoodDataWithGoodItem(): React.Node {
     const sections = [
       {
         key: 'a',
@@ -37,7 +37,7 @@ module.exports = {
     return <SectionList renderItem={renderMyListItem} sections={sections} />;
   },
 
-  testBadRenderItemFunction() {
+  testBadRenderItemFunction(): $TEMPORARY$array<React.Node> {
     const sections = [
       {
         key: 'a',
diff --git a/Libraries/Modal/Modal.js b/Libraries/Modal/Modal.js
index b5282e3bc0070f..e21ed2ced51564 100644
--- a/Libraries/Modal/Modal.js
+++ b/Libraries/Modal/Modal.js
@@ -12,18 +12,17 @@
 
 const AppContainer = require('../ReactNative/AppContainer');
 const I18nManager = require('../ReactNative/I18nManager');
-const React = require('react');
 const PropTypes = require('prop-types');
+const React = require('react');
 const ScrollView = require('../Components/ScrollView/ScrollView');
 const StyleSheet = require('../StyleSheet/StyleSheet');
 const View = require('../Components/View/View');
 
-import RCTModalHostView from './RCTModalHostViewNativeComponent';
-
-import type EmitterSubscription from '../vendor/emitter/EmitterSubscription';
 import type {ViewProps} from '../Components/View/ViewPropTypes';
-import type {SyntheticEvent} from '../Types/CoreEventTypes';
 import type {DirectEventHandler} from '../Types/CodegenTypes';
+import type {SyntheticEvent} from '../Types/CoreEventTypes';
+import type EmitterSubscription from '../vendor/emitter/EmitterSubscription';
+import RCTModalHostView from './RCTModalHostViewNativeComponent';
 /**
  * The Modal component is a simple way to present content above an enclosing view.
  *
@@ -138,12 +137,17 @@ export type Props = $ReadOnly<{|
 |}>;
 
 class Modal extends React.Component<Props> {
-  static defaultProps = {
+  static defaultProps: $TEMPORARY$object<{|
+    hardwareAccelerated: boolean,
+    visible: boolean,
+  |}> = {
     visible: true,
     hardwareAccelerated: false,
   };
 
-  static contextTypes = {
+  static contextTypes:
+    | any
+    | $TEMPORARY$object<{|rootTag: React$PropType$Primitive<number>|}> = {
     rootTag: PropTypes.number,
   };
 
@@ -156,11 +160,13 @@ class Modal extends React.Component<Props> {
     this._identifier = uniqueModalIdentifier++;
   }
 
-  static childContextTypes = {
+  static childContextTypes:
+    | any
+    | $TEMPORARY$object<{|virtualizedList: React$PropType$Primitive<any>|}> = {
     virtualizedList: PropTypes.object,
   };
 
-  getChildContext() {
+  getChildContext(): $TEMPORARY$object<{|virtualizedList: null|}> {
     // Reset the context so VirtualizedList doesn't get confused by nesting
     // in the React tree that doesn't reflect the native component hierarchy.
     return {
diff --git a/Libraries/Modal/NativeModalManager.js b/Libraries/Modal/NativeModalManager.js
index d293caf68f45c3..5f4e6c146fcc0e 100644
--- a/Libraries/Modal/NativeModalManager.js
+++ b/Libraries/Modal/NativeModalManager.js
@@ -19,4 +19,4 @@ export interface Spec extends TurboModule {
   +removeListeners: (count: number) => void;
 }
 
-export default TurboModuleRegistry.get<Spec>('ModalManager');
+export default (TurboModuleRegistry.get<Spec>('ModalManager'): ?Spec);
diff --git a/Libraries/NativeModules/specs/NativeAnimationsDebugModule.js b/Libraries/NativeModules/specs/NativeAnimationsDebugModule.js
index cb653ffe9ad0b4..f814d567df056a 100644
--- a/Libraries/NativeModules/specs/NativeAnimationsDebugModule.js
+++ b/Libraries/NativeModules/specs/NativeAnimationsDebugModule.js
@@ -18,4 +18,4 @@ export interface Spec extends TurboModule {
   +stopRecordingFps: (animationStopTimeMs: number) => void;
 }
 
-export default TurboModuleRegistry.get<Spec>('AnimationsDebugModule');
+export default (TurboModuleRegistry.get<Spec>('AnimationsDebugModule'): ?Spec);
diff --git a/Libraries/NativeModules/specs/NativeDevSettings.js b/Libraries/NativeModules/specs/NativeDevSettings.js
index 9a53a0db7905e0..ec0f9392e8c492 100644
--- a/Libraries/NativeModules/specs/NativeDevSettings.js
+++ b/Libraries/NativeModules/specs/NativeDevSettings.js
@@ -25,4 +25,4 @@ export interface Spec extends TurboModule {
   +setIsShakeToShowDevMenuEnabled: (enabled: boolean) => void;
 }
 
-export default TurboModuleRegistry.getEnforcing<Spec>('DevSettings');
+export default (TurboModuleRegistry.getEnforcing<Spec>('DevSettings'): Spec);
diff --git a/Libraries/NativeModules/specs/NativeDeviceEventManager.js b/Libraries/NativeModules/specs/NativeDeviceEventManager.js
index 1755ba1fc403a8..342115dd0e478e 100644
--- a/Libraries/NativeModules/specs/NativeDeviceEventManager.js
+++ b/Libraries/NativeModules/specs/NativeDeviceEventManager.js
@@ -17,4 +17,4 @@ export interface Spec extends TurboModule {
   +invokeDefaultBackPressHandler: () => void;
 }
 
-export default TurboModuleRegistry.get<Spec>('DeviceEventManager');
+export default (TurboModuleRegistry.get<Spec>('DeviceEventManager'): ?Spec);
diff --git a/Libraries/NativeModules/specs/NativeDialogManagerAndroid.js b/Libraries/NativeModules/specs/NativeDialogManagerAndroid.js
index d1bc7959f7ddda..4ca12692fa1773 100644
--- a/Libraries/NativeModules/specs/NativeDialogManagerAndroid.js
+++ b/Libraries/NativeModules/specs/NativeDialogManagerAndroid.js
@@ -46,4 +46,4 @@ export interface Spec extends TurboModule {
   ) => void;
 }
 
-export default TurboModuleRegistry.get<Spec>('DialogManagerAndroid');
+export default (TurboModuleRegistry.get<Spec>('DialogManagerAndroid'): ?Spec);
diff --git a/Libraries/NativeModules/specs/NativeRedBox.js b/Libraries/NativeModules/specs/NativeRedBox.js
index 336caca5dcf5d0..e132b544345324 100644
--- a/Libraries/NativeModules/specs/NativeRedBox.js
+++ b/Libraries/NativeModules/specs/NativeRedBox.js
@@ -18,4 +18,4 @@ export interface Spec extends TurboModule {
   +dismiss: () => void;
 }
 
-export default TurboModuleRegistry.get<Spec>('RedBox');
+export default (TurboModuleRegistry.get<Spec>('RedBox'): ?Spec);
diff --git a/Libraries/NativeModules/specs/NativeSourceCode.js b/Libraries/NativeModules/specs/NativeSourceCode.js
index e0383ace4a87d3..2ba94687afb6ea 100644
--- a/Libraries/NativeModules/specs/NativeSourceCode.js
+++ b/Libraries/NativeModules/specs/NativeSourceCode.js
@@ -19,4 +19,4 @@ export interface Spec extends TurboModule {
   |};
 }
 
-export default TurboModuleRegistry.getEnforcing<Spec>('SourceCode');
+export default (TurboModuleRegistry.getEnforcing<Spec>('SourceCode'): Spec);
diff --git a/Libraries/Network/NativeNetworkingAndroid.js b/Libraries/Network/NativeNetworkingAndroid.js
index 6b0eded7289dac..573090d7d26ccd 100644
--- a/Libraries/Network/NativeNetworkingAndroid.js
+++ b/Libraries/Network/NativeNetworkingAndroid.js
@@ -35,4 +35,4 @@ export interface Spec extends TurboModule {
   +removeListeners: (count: number) => void;
 }
 
-export default TurboModuleRegistry.getEnforcing<Spec>('Networking');
+export default (TurboModuleRegistry.getEnforcing<Spec>('Networking'): Spec);
diff --git a/Libraries/Network/NativeNetworkingIOS.js b/Libraries/Network/NativeNetworkingIOS.js
index 8a2269c6dcaff0..85a6cffbd22034 100644
--- a/Libraries/Network/NativeNetworkingIOS.js
+++ b/Libraries/Network/NativeNetworkingIOS.js
@@ -35,4 +35,4 @@ export interface Spec extends TurboModule {
   +removeListeners: (count: number) => void;
 }
 
-export default TurboModuleRegistry.getEnforcing<Spec>('Networking');
+export default (TurboModuleRegistry.getEnforcing<Spec>('Networking'): Spec);
diff --git a/Libraries/Network/RCTNetworking.ios.js b/Libraries/Network/RCTNetworking.ios.js
index 3abaeb0b0c3c34..73a33ab1d9fbe5 100644
--- a/Libraries/Network/RCTNetworking.ios.js
+++ b/Libraries/Network/RCTNetworking.ios.js
@@ -11,12 +11,12 @@
 'use strict';
 
 const NativeEventEmitter = require('../EventEmitter/NativeEventEmitter');
-import NativeNetworkingIOS from './NativeNetworkingIOS';
-const convertRequestBody = require('./convertRequestBody');
 
-import type {RequestBody} from './convertRequestBody';
+const convertRequestBody = require('./convertRequestBody');
 
+import NativeNetworkingIOS from './NativeNetworkingIOS';
 import type {NativeResponseType} from './XMLHttpRequest';
+import type {RequestBody} from './convertRequestBody';
 
 class RCTNetworking extends NativeEventEmitter {
   constructor() {
@@ -60,4 +60,4 @@ class RCTNetworking extends NativeEventEmitter {
   }
 }
 
-module.exports = new RCTNetworking();
+module.exports = (new RCTNetworking(): RCTNetworking);
diff --git a/Libraries/Network/XMLHttpRequest.js b/Libraries/Network/XMLHttpRequest.js
index f0f507cd873895..14e06222b684d8 100644
--- a/Libraries/Network/XMLHttpRequest.js
+++ b/Libraries/Network/XMLHttpRequest.js
@@ -10,13 +10,13 @@
 
 'use strict';
 
+const BlobManager = require('../Blob/BlobManager');
 const EventTarget = require('event-target-shim');
 const RCTNetworking = require('./RCTNetworking');
 
 const base64 = require('base64-js');
 const invariant = require('invariant');
 const warning = require('fbjs/lib/warning');
-const BlobManager = require('../Blob/BlobManager');
 
 export type NativeResponseType = 'base64' | 'blob' | 'text';
 export type ResponseType =
@@ -73,7 +73,7 @@ const REQUEST_EVENTS = [
 
 const XHR_EVENTS = REQUEST_EVENTS.concat('readystatechange');
 
-class XMLHttpRequestEventTarget extends EventTarget(...REQUEST_EVENTS) {
+class XMLHttpRequestEventTarget extends (EventTarget(...REQUEST_EVENTS): any) {
   onload: ?Function;
   onloadstart: ?Function;
   onprogress: ?Function;
@@ -86,7 +86,7 @@ class XMLHttpRequestEventTarget extends EventTarget(...REQUEST_EVENTS) {
 /**
  * Shared base for platform-specific XMLHttpRequest implementations.
  */
-class XMLHttpRequest extends EventTarget(...XHR_EVENTS) {
+class XMLHttpRequest extends (EventTarget(...XHR_EVENTS): any) {
   static UNSENT: number = UNSENT;
   static OPENED: number = OPENED;
   static HEADERS_RECEIVED: number = HEADERS_RECEIVED;
diff --git a/Libraries/Performance/NativeJSCSamplingProfiler.js b/Libraries/Performance/NativeJSCSamplingProfiler.js
index 944d68383bcefa..a40e8e301520b8 100644
--- a/Libraries/Performance/NativeJSCSamplingProfiler.js
+++ b/Libraries/Performance/NativeJSCSamplingProfiler.js
@@ -17,4 +17,4 @@ export interface Spec extends TurboModule {
   +operationComplete: (token: number, result: ?string, error: ?string) => void;
 }
 
-export default TurboModuleRegistry.get<Spec>('JSCSamplingProfiler');
+export default (TurboModuleRegistry.get<Spec>('JSCSamplingProfiler'): ?Spec);
diff --git a/Libraries/PermissionsAndroid/NativePermissionsAndroid.js b/Libraries/PermissionsAndroid/NativePermissionsAndroid.js
index 4212164d8baf83..685cb56be00e6d 100644
--- a/Libraries/PermissionsAndroid/NativePermissionsAndroid.js
+++ b/Libraries/PermissionsAndroid/NativePermissionsAndroid.js
@@ -56,4 +56,4 @@ export interface Spec extends TurboModule {
   ) => Promise<{[permission: PermissionType]: PermissionStatus}>;
 }
 
-export default TurboModuleRegistry.get<Spec>('PermissionsAndroid');
+export default (TurboModuleRegistry.get<Spec>('PermissionsAndroid'): ?Spec);
diff --git a/Libraries/PermissionsAndroid/PermissionsAndroid.js b/Libraries/PermissionsAndroid/PermissionsAndroid.js
index 427fb21c8a1f88..9ba1624c62b852 100644
--- a/Libraries/PermissionsAndroid/PermissionsAndroid.js
+++ b/Libraries/PermissionsAndroid/PermissionsAndroid.js
@@ -10,16 +10,15 @@
 
 'use strict';
 
-import NativeDialogManagerAndroid from '../NativeModules/specs/NativeDialogManagerAndroid';
 const Platform = require('../Utilities/Platform');
-import NativePermissionsAndroid from './NativePermissionsAndroid';
-
-import invariant from 'invariant';
 
+import NativeDialogManagerAndroid from '../NativeModules/specs/NativeDialogManagerAndroid';
+import NativePermissionsAndroid from './NativePermissionsAndroid';
 import type {
   PermissionStatus,
   PermissionType,
 } from './NativePermissionsAndroid';
+import invariant from 'invariant';
 
 export type Rationale = {
   title: string,
@@ -69,8 +68,37 @@ const PERMISSIONS = Object.freeze({
  */
 
 class PermissionsAndroid {
-  PERMISSIONS = PERMISSIONS;
-  RESULTS = PERMISSION_REQUEST_RESULT;
+  PERMISSIONS: {|
+    ACCESS_COARSE_LOCATION: string,
+    ACCESS_FINE_LOCATION: string,
+    ADD_VOICEMAIL: string,
+    BODY_SENSORS: string,
+    CALL_PHONE: string,
+    CAMERA: string,
+    GET_ACCOUNTS: string,
+    PROCESS_OUTGOING_CALLS: string,
+    READ_CALENDAR: string,
+    READ_CALL_LOG: string,
+    READ_CONTACTS: string,
+    READ_EXTERNAL_STORAGE: string,
+    READ_PHONE_STATE: string,
+    READ_SMS: string,
+    RECEIVE_MMS: string,
+    RECEIVE_SMS: string,
+    RECEIVE_WAP_PUSH: string,
+    RECORD_AUDIO: string,
+    SEND_SMS: string,
+    USE_SIP: string,
+    WRITE_CALENDAR: string,
+    WRITE_CALL_LOG: string,
+    WRITE_CONTACTS: string,
+    WRITE_EXTERNAL_STORAGE: string,
+  |} = PERMISSIONS;
+  RESULTS: {|
+    DENIED: $TEMPORARY$string<'denied'>,
+    GRANTED: $TEMPORARY$string<'granted'>,
+    NEVER_ASK_AGAIN: $TEMPORARY$string<'never_ask_again'>,
+  |} = PERMISSION_REQUEST_RESULT;
 
   /**
    * DEPRECATED - use check
diff --git a/Libraries/PushNotificationIOS/NativePushNotificationManagerIOS.js b/Libraries/PushNotificationIOS/NativePushNotificationManagerIOS.js
index 8d7ea0adbf7144..8eb5095163681c 100644
--- a/Libraries/PushNotificationIOS/NativePushNotificationManagerIOS.js
+++ b/Libraries/PushNotificationIOS/NativePushNotificationManagerIOS.js
@@ -8,8 +8,8 @@
  * @flow
  */
 
-import * as TurboModuleRegistry from '../TurboModule/TurboModuleRegistry';
 import type {TurboModule} from '../TurboModule/RCTExport';
+import * as TurboModuleRegistry from '../TurboModule/TurboModuleRegistry';
 
 type Permissions = {|
   alert: boolean,
@@ -69,4 +69,6 @@ export interface Spec extends TurboModule {
   +removeListeners: (count: number) => void;
 }
 
-export default TurboModuleRegistry.get<Spec>('PushNotificationManager');
+export default (TurboModuleRegistry.get<Spec>(
+  'PushNotificationManager',
+): ?Spec);
diff --git a/Libraries/ReactNative/AppContainer.js b/Libraries/ReactNative/AppContainer.js
index a5e792de7c564a..39d3374a864a1d 100644
--- a/Libraries/ReactNative/AppContainer.js
+++ b/Libraries/ReactNative/AppContainer.js
@@ -42,7 +42,9 @@ class AppContainer extends React.Component<Props, State> {
   _mainRef: ?React.ElementRef<typeof View>;
   _subscription: ?EmitterSubscription = null;
 
-  static childContextTypes = {
+  static childContextTypes:
+    | any
+    | $TEMPORARY$object<{|rootTag: React$PropType$Primitive<number>|}> = {
     rootTag: PropTypes.number,
   };
 
diff --git a/Libraries/ReactNative/DummyUIManager.js b/Libraries/ReactNative/DummyUIManager.js
index 38f93adc54a016..fb2a774b916fd9 100644
--- a/Libraries/ReactNative/DummyUIManager.js
+++ b/Libraries/ReactNative/DummyUIManager.js
@@ -10,15 +10,15 @@
 'use strict';
 
 module.exports = {
-  getViewManagerConfig: (viewManagerName: string) => {
+  getViewManagerConfig: (viewManagerName: string): null => {
     console.warn(
       'Attempting to get config for view manager: ' + viewManagerName,
     );
     return null;
   },
-  getConstants: () => ({}),
+  getConstants: (): $TEMPORARY$object<{||}> => ({}),
   getConstantsForViewManager: (viewManagerName: string) => {},
-  getDefaultEventTypes: () => [],
+  getDefaultEventTypes: (): Array<$FlowFixMe> => [],
   playTouchSound: () => {},
   lazilyLoadView: (name: string) => {},
   createView: (
diff --git a/Libraries/ReactNative/I18nManager.js b/Libraries/ReactNative/I18nManager.js
index f5616c807ae57e..94133b1dd1f421 100644
--- a/Libraries/ReactNative/I18nManager.js
+++ b/Libraries/ReactNative/I18nManager.js
@@ -11,7 +11,10 @@
 
 import NativeI18nManager from './NativeI18nManager';
 
-const i18nConstants = NativeI18nManager
+const i18nConstants: {|
+  doLeftAndRightSwapInRTL: boolean,
+  isRTL: boolean,
+|} = NativeI18nManager
   ? NativeI18nManager.getConstants()
   : {
       isRTL: false,
@@ -19,7 +22,7 @@ const i18nConstants = NativeI18nManager
     };
 
 module.exports = {
-  getConstants: () => {
+  getConstants: (): {|doLeftAndRightSwapInRTL: boolean, isRTL: boolean|} => {
     return i18nConstants;
   },
 
diff --git a/Libraries/ReactNative/NativeHeadlessJsTaskSupport.js b/Libraries/ReactNative/NativeHeadlessJsTaskSupport.js
index d3256f49e10046..290957fd7f2414 100644
--- a/Libraries/ReactNative/NativeHeadlessJsTaskSupport.js
+++ b/Libraries/ReactNative/NativeHeadlessJsTaskSupport.js
@@ -18,4 +18,4 @@ export interface Spec extends TurboModule {
   +notifyTaskRetry: (taskId: number) => Promise<boolean>;
 }
 
-export default TurboModuleRegistry.get<Spec>('HeadlessJsTaskSupport');
+export default (TurboModuleRegistry.get<Spec>('HeadlessJsTaskSupport'): ?Spec);
diff --git a/Libraries/ReactNative/NativeI18nManager.js b/Libraries/ReactNative/NativeI18nManager.js
index 9da9a6ade2b960..afaab21dfce13f 100644
--- a/Libraries/ReactNative/NativeI18nManager.js
+++ b/Libraries/ReactNative/NativeI18nManager.js
@@ -23,4 +23,4 @@ export interface Spec extends TurboModule {
   swapLeftAndRightInRTL: (flipStyles: boolean) => void;
 }
 
-export default TurboModuleRegistry.get<Spec>('I18nManager');
+export default (TurboModuleRegistry.get<Spec>('I18nManager'): ?Spec);
diff --git a/Libraries/ReactNative/NativeUIManager.js b/Libraries/ReactNative/NativeUIManager.js
index ad6740747b5c70..717e63dbc12282 100644
--- a/Libraries/ReactNative/NativeUIManager.js
+++ b/Libraries/ReactNative/NativeUIManager.js
@@ -119,4 +119,4 @@ export interface Spec extends TurboModule {
   +dismissPopupMenu: () => void;
 }
 
-export default TurboModuleRegistry.getEnforcing<Spec>('UIManager');
+export default (TurboModuleRegistry.getEnforcing<Spec>('UIManager'): Spec);
diff --git a/Libraries/ReactNative/PaperUIManager.js b/Libraries/ReactNative/PaperUIManager.js
index 5e80795ec2990f..9d2a65aded3fd4 100644
--- a/Libraries/ReactNative/PaperUIManager.js
+++ b/Libraries/ReactNative/PaperUIManager.js
@@ -36,7 +36,7 @@ const UIManagerJS = {
   getConstants(): Object {
     return getConstants();
   },
-  getViewManagerConfig: function(viewManagerName: string) {
+  getViewManagerConfig: function(viewManagerName: string): any {
     if (
       viewManagerConfigs[viewManagerName] === undefined &&
       NativeUIManager.getConstantsForViewManager
diff --git a/Libraries/ReactNative/RootTagContext.js b/Libraries/ReactNative/RootTagContext.js
index f85a8c73ea0a35..ca5ed03932fd5c 100644
--- a/Libraries/ReactNative/RootTagContext.js
+++ b/Libraries/ReactNative/RootTagContext.js
@@ -12,4 +12,4 @@
 
 const React = require('react');
 
-module.exports = React.createContext<number>(0);
+module.exports = (React.createContext<number>(0): React$Context<number>);
diff --git a/Libraries/ReactNative/getNativeComponentAttributes.js b/Libraries/ReactNative/getNativeComponentAttributes.js
index 9dba82c47507e4..226e3ba9342b42 100644
--- a/Libraries/ReactNative/getNativeComponentAttributes.js
+++ b/Libraries/ReactNative/getNativeComponentAttributes.js
@@ -14,16 +14,16 @@ const ReactNativeStyleAttributes = require('../Components/View/ReactNativeStyleA
 const UIManager = require('./UIManager');
 
 const insetsDiffer = require('../Utilities/differ/insetsDiffer');
+const invariant = require('invariant');
 const matricesDiffer = require('../Utilities/differ/matricesDiffer');
 const pointsDiffer = require('../Utilities/differ/pointsDiffer');
 const processColor = require('../StyleSheet/processColor');
 const processColorArray = require('../StyleSheet/processColorArray');
 const resolveAssetSource = require('../Image/resolveAssetSource');
 const sizesDiffer = require('../Utilities/differ/sizesDiffer');
-const invariant = require('invariant');
 const warning = require('fbjs/lib/warning');
 
-function getNativeComponentAttributes(uiViewClassName: string) {
+function getNativeComponentAttributes(uiViewClassName: string): any {
   const viewConfig = UIManager.getViewManagerConfig(uiViewClassName);
 
   invariant(
diff --git a/Libraries/Renderer/shims/ReactNativeViewConfigRegistry.js b/Libraries/Renderer/shims/ReactNativeViewConfigRegistry.js
index 5ebc0d36d39fee..c1e192abae644b 100644
--- a/Libraries/Renderer/shims/ReactNativeViewConfigRegistry.js
+++ b/Libraries/Renderer/shims/ReactNativeViewConfigRegistry.js
@@ -20,8 +20,8 @@ import type {
 const invariant = require('invariant');
 
 // Event configs
-const customBubblingEventTypes = {};
-const customDirectEventTypes = {};
+const customBubblingEventTypes: $TEMPORARY$object<{||}> = {};
+const customDirectEventTypes: $TEMPORARY$object<{||}> = {};
 
 exports.customBubblingEventTypes = customBubblingEventTypes;
 exports.customDirectEventTypes = customDirectEventTypes;
diff --git a/Libraries/Settings/NativeSettingsManager.js b/Libraries/Settings/NativeSettingsManager.js
index 19de825248cdb9..1edd6187218962 100644
--- a/Libraries/Settings/NativeSettingsManager.js
+++ b/Libraries/Settings/NativeSettingsManager.js
@@ -21,4 +21,6 @@ export interface Spec extends TurboModule {
   +deleteValues: (values: Array<string>) => void;
 }
 
-export default TurboModuleRegistry.getEnforcing<Spec>('SettingsManager');
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'SettingsManager',
+): Spec);
diff --git a/Libraries/Settings/Settings.ios.js b/Libraries/Settings/Settings.ios.js
index c802759f764d1b..55d8ff0481d2e1 100644
--- a/Libraries/Settings/Settings.ios.js
+++ b/Libraries/Settings/Settings.ios.js
@@ -11,15 +11,16 @@
 'use strict';
 
 const RCTDeviceEventEmitter = require('../EventEmitter/RCTDeviceEventEmitter');
-import NativeSettingsManager from './NativeSettingsManager';
 
 const invariant = require('invariant');
 
+import NativeSettingsManager from './NativeSettingsManager';
+
 const subscriptions: Array<{keys: Array<string>, callback: ?Function}> = [];
 
 const Settings = {
-  _settings:
-    NativeSettingsManager && NativeSettingsManager.getConstants().settings,
+  _settings: (NativeSettingsManager &&
+    NativeSettingsManager.getConstants().settings: any),
 
   get(key: string): mixed {
     return this._settings[key];
diff --git a/Libraries/Share/NativeShareModule.js b/Libraries/Share/NativeShareModule.js
index 291a0e01cfaef6..88293b8ce87bac 100644
--- a/Libraries/Share/NativeShareModule.js
+++ b/Libraries/Share/NativeShareModule.js
@@ -21,4 +21,4 @@ export interface Spec extends TurboModule {
   ) => Promise<{|action: string|}>;
 }
 
-export default TurboModuleRegistry.get<Spec>('ShareModule');
+export default (TurboModuleRegistry.get<Spec>('ShareModule'): ?Spec);
diff --git a/Libraries/Storage/NativeAsyncStorage.js b/Libraries/Storage/NativeAsyncStorage.js
index a1c4e51ff9bbca..e7c8e567bbfefd 100644
--- a/Libraries/Storage/NativeAsyncStorage.js
+++ b/Libraries/Storage/NativeAsyncStorage.js
@@ -40,5 +40,5 @@ export interface Spec extends TurboModule {
   ) => void;
 }
 
-export default TurboModuleRegistry.get<Spec>('AsyncSQLiteDBStorage') ||
-  TurboModuleRegistry.get<Spec>('AsyncLocalStorage');
+export default (TurboModuleRegistry.get<Spec>('AsyncSQLiteDBStorage') ||
+  TurboModuleRegistry.get<Spec>('AsyncLocalStorage'): ?Spec);
diff --git a/Libraries/StyleSheet/StyleSheet.js b/Libraries/StyleSheet/StyleSheet.js
index 3c3352e37df389..deb6d8cc4e837a 100644
--- a/Libraries/StyleSheet/StyleSheet.js
+++ b/Libraries/StyleSheet/StyleSheet.js
@@ -151,7 +151,7 @@ export type ImageStyle = ____ImageStyle_Internal;
  */
 export type DangerouslyImpreciseStyle = ____DangerouslyImpreciseStyle_Internal;
 
-let hairlineWidth = PixelRatio.roundToNearestPixel(0.4);
+let hairlineWidth: number = PixelRatio.roundToNearestPixel(0.4);
 if (hairlineWidth === 0) {
   hairlineWidth = 1 / PixelRatio.get();
 }
diff --git a/Libraries/Text/TextAncestor.js b/Libraries/Text/TextAncestor.js
index 5a8e79eee2ca7a..24fb1b45512fad 100644
--- a/Libraries/Text/TextAncestor.js
+++ b/Libraries/Text/TextAncestor.js
@@ -18,4 +18,4 @@ const React = require('react');
 /* $FlowFixMe(>=0.85.0 site=react_native_fb) This comment suppresses an error
  * found when Flow v0.85 was deployed. To see the error, delete this comment
  * and run Flow. */
-module.exports = React.createContext(false);
+module.exports = (React.createContext(false): React$Context<$FlowFixMe>);
diff --git a/Libraries/Text/TextPropTypes.js b/Libraries/Text/TextPropTypes.js
index 756d95721f1b27..216ac303f84fe8 100644
--- a/Libraries/Text/TextPropTypes.js
+++ b/Libraries/Text/TextPropTypes.js
@@ -12,11 +12,13 @@
 
 const DeprecatedColorPropType = require('../DeprecatedPropTypes/DeprecatedColorPropType');
 const DeprecatedEdgeInsetsPropType = require('../DeprecatedPropTypes/DeprecatedEdgeInsetsPropType');
-const PropTypes = require('prop-types');
 const DeprecatedStyleSheetPropType = require('../DeprecatedPropTypes/DeprecatedStyleSheetPropType');
+const PropTypes = require('prop-types');
 const TextStylePropTypes = require('./TextStylePropTypes');
 
-const stylePropType = DeprecatedStyleSheetPropType(TextStylePropTypes);
+const stylePropType: ReactPropsCheckType = DeprecatedStyleSheetPropType(
+  TextStylePropTypes,
+);
 
 const DataDetectorTypes = ['phoneNumber', 'link', 'email', 'none', 'all'];
 
@@ -27,7 +29,12 @@ module.exports = {
    *
    * See https://facebook.github.io/react-native/docs/text.html#ellipsizemode
    */
-  ellipsizeMode: PropTypes.oneOf(['head', 'middle', 'tail', 'clip']),
+  ellipsizeMode: (PropTypes.oneOf([
+    'head',
+    'middle',
+    'tail',
+    'clip',
+  ]): React$PropType$Primitive<'head' | 'middle' | 'tail' | 'clip'>),
   /**
    * Used to truncate the text with an ellipsis.
    *
@@ -39,7 +46,11 @@ module.exports = {
    *
    * See https://facebook.github.io/react-native/docs/text.html#textbreakstrategy
    */
-  textBreakStrategy: PropTypes.oneOf(['simple', 'highQuality', 'balanced']),
+  textBreakStrategy: (PropTypes.oneOf([
+    'simple',
+    'highQuality',
+    'balanced',
+  ]): React$PropType$Primitive<'simple' | 'highQuality' | 'balanced'>),
   /**
    * Invoked on mount and layout changes.
    *
@@ -139,5 +150,9 @@ module.exports = {
    *
    * See https://facebook.github.io/react-native/docs/text.html#dataDetectorType
    */
-  dataDetectorType: PropTypes.oneOf(DataDetectorTypes),
+  dataDetectorType: (PropTypes.oneOf(
+    DataDetectorTypes,
+  ): React$PropType$Primitive<
+    'phoneNumber' | 'link' | 'email' | 'none' | 'all',
+  >),
 };
diff --git a/Libraries/Text/TextStylePropTypes.js b/Libraries/Text/TextStylePropTypes.js
index e41f6d833cc5d0..d1ad5ba5bf9c3b 100644
--- a/Libraries/Text/TextStylePropTypes.js
+++ b/Libraries/Text/TextStylePropTypes.js
@@ -11,8 +11,8 @@
 'use strict';
 
 const DeprecatedColorPropType = require('../DeprecatedPropTypes/DeprecatedColorPropType');
-const ReactPropTypes = require('prop-types');
 const DeprecatedViewStylePropTypes = require('../DeprecatedPropTypes/DeprecatedViewStylePropTypes');
+const ReactPropTypes = require('prop-types');
 
 const TextStylePropTypes = {
   ...DeprecatedViewStylePropTypes,
@@ -20,13 +20,16 @@ const TextStylePropTypes = {
   color: DeprecatedColorPropType,
   fontFamily: ReactPropTypes.string,
   fontSize: ReactPropTypes.number,
-  fontStyle: ReactPropTypes.oneOf(['normal', 'italic']),
+  fontStyle: (ReactPropTypes.oneOf([
+    'normal',
+    'italic',
+  ]): React$PropType$Primitive<'normal' | 'italic'>),
   /**
    * Specifies font weight. The values 'normal' and 'bold' are supported for
    * most fonts. Not all fonts have a variant for each of the numeric values,
    * in that case the closest one is chosen.
    */
-  fontWeight: ReactPropTypes.oneOf([
+  fontWeight: (ReactPropTypes.oneOf([
     'normal' /*default*/,
     'bold',
     '100',
@@ -38,11 +41,23 @@ const TextStylePropTypes = {
     '700',
     '800',
     '900',
-  ]),
+  ]): React$PropType$Primitive<
+    | 'normal'
+    | 'bold'
+    | '100'
+    | '200'
+    | '300'
+    | '400'
+    | '500'
+    | '600'
+    | '700'
+    | '800'
+    | '900',
+  >),
   /**
    * @platform ios
    */
-  fontVariant: ReactPropTypes.arrayOf(
+  fontVariant: (ReactPropTypes.arrayOf(
     ReactPropTypes.oneOf([
       'small-caps',
       'oldstyle-nums',
@@ -50,11 +65,19 @@ const TextStylePropTypes = {
       'tabular-nums',
       'proportional-nums',
     ]),
-  ),
-  textShadowOffset: ReactPropTypes.shape({
+  ): React$PropType$Primitive<
+    Array<
+      | 'small-caps'
+      | 'oldstyle-nums'
+      | 'lining-nums'
+      | 'tabular-nums'
+      | 'proportional-nums',
+    >,
+  >),
+  textShadowOffset: (ReactPropTypes.shape({
     width: ReactPropTypes.number,
     height: ReactPropTypes.number,
-  }),
+  }): React$PropType$Primitive<{height?: number, width?: number}>),
   textShadowRadius: ReactPropTypes.number,
   textShadowColor: DeprecatedColorPropType,
   /**
@@ -66,22 +89,24 @@ const TextStylePropTypes = {
    * Specifies text alignment. The value 'justify' is only supported on iOS and
    * fallbacks to `left` on Android.
    */
-  textAlign: ReactPropTypes.oneOf([
+  textAlign: (ReactPropTypes.oneOf([
     'auto' /*default*/,
     'left',
     'right',
     'center',
     'justify',
-  ]),
+  ]): React$PropType$Primitive<
+    'auto' | 'left' | 'right' | 'center' | 'justify',
+  >),
   /**
    * @platform android
    */
-  textAlignVertical: ReactPropTypes.oneOf([
+  textAlignVertical: (ReactPropTypes.oneOf([
     'auto' /*default*/,
     'top',
     'bottom',
     'center',
-  ]),
+  ]): React$PropType$Primitive<'auto' | 'top' | 'bottom' | 'center'>),
   /**
    * Set to `false` to remove extra font padding intended to make space for certain ascenders / descenders.
    * With some fonts, this padding can make text look slightly misaligned when centered vertically.
@@ -89,35 +114,43 @@ const TextStylePropTypes = {
    * @platform android
    */
   includeFontPadding: ReactPropTypes.bool,
-  textDecorationLine: ReactPropTypes.oneOf([
+  textDecorationLine: (ReactPropTypes.oneOf([
     'none' /*default*/,
     'underline',
     'line-through',
     'underline line-through',
-  ]),
+  ]): React$PropType$Primitive<
+    'none' | 'underline' | 'line-through' | 'underline line-through',
+  >),
   /**
    * @platform ios
    */
-  textDecorationStyle: ReactPropTypes.oneOf([
+  textDecorationStyle: (ReactPropTypes.oneOf([
     'solid' /*default*/,
     'double',
     'dotted',
     'dashed',
-  ]),
+  ]): React$PropType$Primitive<'solid' | 'double' | 'dotted' | 'dashed'>),
   /**
    * @platform ios
    */
   textDecorationColor: DeprecatedColorPropType,
-  textTransform: ReactPropTypes.oneOf([
+  textTransform: (ReactPropTypes.oneOf([
     'none' /*default*/,
     'capitalize',
     'uppercase',
     'lowercase',
-  ]),
+  ]): React$PropType$Primitive<
+    'none' | 'capitalize' | 'uppercase' | 'lowercase',
+  >),
   /**
    * @platform ios
    */
-  writingDirection: ReactPropTypes.oneOf(['auto' /*default*/, 'ltr', 'rtl']),
+  writingDirection: (ReactPropTypes.oneOf([
+    'auto' /*default*/,
+    'ltr',
+    'rtl',
+  ]): React$PropType$Primitive<'auto' | 'ltr' | 'rtl'>),
 };
 
 module.exports = TextStylePropTypes;
diff --git a/Libraries/TurboModule/samples/NativeSampleTurboModule.js b/Libraries/TurboModule/samples/NativeSampleTurboModule.js
index 486d555aa04516..f82a8e810878e5 100644
--- a/Libraries/TurboModule/samples/NativeSampleTurboModule.js
+++ b/Libraries/TurboModule/samples/NativeSampleTurboModule.js
@@ -31,4 +31,6 @@ export interface Spec extends TurboModule {
   +getValueWithPromise: (error: boolean) => Promise<string>;
 }
 
-export default TurboModuleRegistry.getEnforcing<Spec>('SampleTurboModule');
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'SampleTurboModule',
+): Spec);
diff --git a/Libraries/UTFSequence.js b/Libraries/UTFSequence.js
index db5ff90fcf8f94..4e6c030ef20f20 100644
--- a/Libraries/UTFSequence.js
+++ b/Libraries/UTFSequence.js
@@ -19,7 +19,22 @@ const deepFreezeAndThrowOnMutationInDev = require('./Utilities/deepFreezeAndThro
  *  - Source code should be limitted to ASCII.
  *  - Less chance of typos.
  */
-const UTFSequence = deepFreezeAndThrowOnMutationInDev({
+const UTFSequence: $TEMPORARY$object<{|
+  BOM: string,
+  BULLET: string,
+  BULLET_SP: string,
+  MDASH: string,
+  MDASH_SP: string,
+  MIDDOT: string,
+  MIDDOT_KATAKANA: string,
+  MIDDOT_SP: string,
+  NBSP: string,
+  NDASH: string,
+  NDASH_SP: string,
+  PIZZA: string,
+  TRIANGLE_LEFT: string,
+  TRIANGLE_RIGHT: string,
+|}> = deepFreezeAndThrowOnMutationInDev({
   BOM: '\ufeff', // byte order mark
   BULLET: '\u2022', // bullet: &#8226;
   BULLET_SP: '\u00A0\u2022\u00A0', // &nbsp;&#8226;&nbsp;
diff --git a/Libraries/Utilities/NativeDevLoadingView.js b/Libraries/Utilities/NativeDevLoadingView.js
index 7141bb660c9a78..e672771778b8a1 100644
--- a/Libraries/Utilities/NativeDevLoadingView.js
+++ b/Libraries/Utilities/NativeDevLoadingView.js
@@ -22,4 +22,4 @@ export interface Spec extends TurboModule {
   +hide: () => void;
 }
 
-export default TurboModuleRegistry.get<Spec>('DevLoadingView');
+export default (TurboModuleRegistry.get<Spec>('DevLoadingView'): ?Spec);
diff --git a/Libraries/Utilities/NativeDeviceInfo.js b/Libraries/Utilities/NativeDeviceInfo.js
index d0cf2eb88087e7..0e42dd6f25d1e5 100644
--- a/Libraries/Utilities/NativeDeviceInfo.js
+++ b/Libraries/Utilities/NativeDeviceInfo.js
@@ -42,7 +42,7 @@ export interface Spec extends TurboModule {
   |};
 }
 
-const NativeModule = TurboModuleRegistry.getEnforcing<Spec>('DeviceInfo');
+const NativeModule: Spec = TurboModuleRegistry.getEnforcing<Spec>('DeviceInfo');
 
 const NativeDeviceInfo = NativeModule;
 
diff --git a/Libraries/Utilities/NativeJSDevSupport.js b/Libraries/Utilities/NativeJSDevSupport.js
index ffbf9aa65595a6..3128d3d83bd214 100644
--- a/Libraries/Utilities/NativeJSDevSupport.js
+++ b/Libraries/Utilities/NativeJSDevSupport.js
@@ -22,4 +22,4 @@ export interface Spec extends TurboModule {
   +onFailure: (errorCode: number, error: string) => void;
 }
 
-export default TurboModuleRegistry.get<Spec>('JSDevSupport');
+export default (TurboModuleRegistry.get<Spec>('JSDevSupport'): ?Spec);
diff --git a/Libraries/Utilities/NativePlatformConstantsAndroid.js b/Libraries/Utilities/NativePlatformConstantsAndroid.js
index ba952618b95600..dcf276ae2ac3f4 100644
--- a/Libraries/Utilities/NativePlatformConstantsAndroid.js
+++ b/Libraries/Utilities/NativePlatformConstantsAndroid.js
@@ -33,4 +33,6 @@ export interface Spec extends TurboModule {
   +getAndroidID: () => string;
 }
 
-export default TurboModuleRegistry.getEnforcing<Spec>('PlatformConstants');
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'PlatformConstants',
+): Spec);
diff --git a/Libraries/Utilities/NativePlatformConstantsIOS.js b/Libraries/Utilities/NativePlatformConstantsIOS.js
index b350a6ee477b67..fd73bcffadb93b 100644
--- a/Libraries/Utilities/NativePlatformConstantsIOS.js
+++ b/Libraries/Utilities/NativePlatformConstantsIOS.js
@@ -29,4 +29,6 @@ export interface Spec extends TurboModule {
   |};
 }
 
-export default TurboModuleRegistry.getEnforcing<Spec>('PlatformConstants');
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'PlatformConstants',
+): Spec);
diff --git a/Libraries/Utilities/Platform.ios.js b/Libraries/Utilities/Platform.ios.js
index 0bdb6d35a621d5..17e1caf389f5a4 100644
--- a/Libraries/Utilities/Platform.ios.js
+++ b/Libraries/Utilities/Platform.ios.js
@@ -20,25 +20,37 @@ export type PlatformSelectSpec<D, I> = {
 const Platform = {
   __constants: null,
   OS: 'ios',
-  get Version() {
+  get Version(): $FlowFixMe {
     return this.constants.osVersion;
   },
-  get constants() {
+  get constants(): {|
+    forceTouchAvailable: boolean,
+    interfaceIdiom: string,
+    isTesting: boolean,
+    osVersion: string,
+    reactNativeVersion: {|
+      major: number,
+      minor: number,
+      patch: number,
+      prerelease: ?number,
+    |},
+    systemName: string,
+  |} {
     if (this.__constants == null) {
       this.__constants = NativePlatformConstantsIOS.getConstants();
     }
     return this.__constants;
   },
-  get isPad() {
+  get isPad(): boolean {
     return this.constants.interfaceIdiom === 'pad';
   },
   /**
    * Deprecated, use `isTV` instead.
    */
-  get isTVOS() {
+  get isTVOS(): boolean {
     return Platform.isTV;
   },
-  get isTV() {
+  get isTV(): boolean {
     return this.constants.interfaceIdiom === 'tv';
   },
   get isTesting(): boolean {
diff --git a/Libraries/Utilities/ReactNativeTestTools.js b/Libraries/Utilities/ReactNativeTestTools.js
index 6028bd94ba5026..a245134b674c95 100644
--- a/Libraries/Utilities/ReactNativeTestTools.js
+++ b/Libraries/Utilities/ReactNativeTestTools.js
@@ -108,12 +108,12 @@ function maximumDepthOfJSON(node: ReactTestRendererNode): number {
   }
 }
 
-function renderAndEnforceStrictMode(element: React.Node) {
+function renderAndEnforceStrictMode(element: React.Node): any {
   expectNoConsoleError();
   return renderWithStrictMode(element);
 }
 
-function renderWithStrictMode(element: React.Node) {
+function renderWithStrictMode(element: React.Node): any {
   const WorkAroundBugWithStrictModeInTestRenderer = prps => prps.children;
   const StrictMode = (React: $FlowFixMe).StrictMode;
   return ReactTestRenderer.create(
diff --git a/Libraries/Utilities/binaryToBase64.js b/Libraries/Utilities/binaryToBase64.js
index 430fd46be68447..19d23d125d2249 100644
--- a/Libraries/Utilities/binaryToBase64.js
+++ b/Libraries/Utilities/binaryToBase64.js
@@ -12,7 +12,7 @@
 
 const base64 = require('base64-js');
 
-function binaryToBase64(data: ArrayBuffer | $ArrayBufferView) {
+function binaryToBase64(data: ArrayBuffer | $ArrayBufferView): any {
   if (data instanceof ArrayBuffer) {
     data = new Uint8Array(data);
   }
diff --git a/Libraries/Utilities/differ/insetsDiffer.js b/Libraries/Utilities/differ/insetsDiffer.js
index 4ebf9746260ff8..53c9d9605c4a02 100644
--- a/Libraries/Utilities/differ/insetsDiffer.js
+++ b/Libraries/Utilities/differ/insetsDiffer.js
@@ -24,7 +24,7 @@ const dummyInsets = {
   bottom: undefined,
 };
 
-const insetsDiffer = function(one: Inset, two: Inset) {
+const insetsDiffer = function(one: Inset, two: Inset): boolean {
   one = one || dummyInsets;
   two = two || dummyInsets;
   return (
diff --git a/Libraries/Utilities/verifyComponentAttributeEquivalence.js b/Libraries/Utilities/verifyComponentAttributeEquivalence.js
index a4db5ef2d252ab..98a725ab02e319 100644
--- a/Libraries/Utilities/verifyComponentAttributeEquivalence.js
+++ b/Libraries/Utilities/verifyComponentAttributeEquivalence.js
@@ -12,8 +12,8 @@
 
 const getNativeComponentAttributes = require('../ReactNative/getNativeComponentAttributes');
 
-import type {ReactNativeBaseComponentViewConfig} from '../Renderer/shims/ReactNativeTypes';
 import ReactNativeViewViewConfig from '../Components/View/ReactNativeViewViewConfig';
+import type {ReactNativeBaseComponentViewConfig} from '../Renderer/shims/ReactNativeTypes';
 
 const IGNORED_KEYS = ['transform', 'hitSlop'];
 /**
@@ -105,7 +105,7 @@ export function lefthandObjectDiff(leftObj: Object, rightObj: Object): Object {
 export function getConfigWithoutViewProps(
   viewConfig: ReactNativeBaseComponentViewConfig<>,
   propName: string,
-) {
+): $TEMPORARY$object<{||}> {
   if (!viewConfig[propName]) {
     return {};
   }
@@ -118,7 +118,7 @@ export function getConfigWithoutViewProps(
     }, {});
 }
 
-export function stringifyViewConfig(viewConfig: any) {
+export function stringifyViewConfig(viewConfig: any): string {
   return JSON.stringify(
     viewConfig,
     (key, val) => {
diff --git a/Libraries/Vibration/NativeVibration.js b/Libraries/Vibration/NativeVibration.js
index 45f9fbd30a3bf4..1416925da5447e 100644
--- a/Libraries/Vibration/NativeVibration.js
+++ b/Libraries/Vibration/NativeVibration.js
@@ -22,4 +22,4 @@ export interface Spec extends TurboModule {
   +cancel: () => void;
 }
 
-export default TurboModuleRegistry.getEnforcing<Spec>('Vibration');
+export default (TurboModuleRegistry.getEnforcing<Spec>('Vibration'): Spec);
diff --git a/Libraries/WebSocket/NativeWebSocketModule.js b/Libraries/WebSocket/NativeWebSocketModule.js
index 0b595b51b02861..da2c57fdabca6e 100644
--- a/Libraries/WebSocket/NativeWebSocketModule.js
+++ b/Libraries/WebSocket/NativeWebSocketModule.js
@@ -30,4 +30,6 @@ export interface Spec extends TurboModule {
   +removeListeners: (count: number) => void;
 }
 
-export default TurboModuleRegistry.getEnforcing<Spec>('WebSocketModule');
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'WebSocketModule',
+): Spec);
diff --git a/Libraries/WebSocket/WebSocket.js b/Libraries/WebSocket/WebSocket.js
index ccca07c77f2080..35f0757b4dc691 100644
--- a/Libraries/WebSocket/WebSocket.js
+++ b/Libraries/WebSocket/WebSocket.js
@@ -11,9 +11,9 @@
 'use strict';
 
 const Blob = require('../Blob/Blob');
+const BlobManager = require('../Blob/BlobManager');
 const EventTarget = require('event-target-shim');
 const NativeEventEmitter = require('../EventEmitter/NativeEventEmitter');
-const BlobManager = require('../Blob/BlobManager');
 const Platform = require('../Utilities/Platform');
 const WebSocketEvent = require('./WebSocketEvent');
 
@@ -21,9 +21,8 @@ const base64 = require('base64-js');
 const binaryToBase64 = require('../Utilities/binaryToBase64');
 const invariant = require('invariant');
 
-import NativeWebSocketModule from './NativeWebSocketModule';
-
 import type EventSubscription from '../vendor/emitter/EventSubscription';
+import NativeWebSocketModule from './NativeWebSocketModule';
 
 type ArrayBufferView =
   | Int8Array
@@ -56,11 +55,11 @@ let nextWebSocketId = 0;
  * See https://developer.mozilla.org/en-US/docs/Web/API/WebSocket
  * See https://github.com/websockets/ws
  */
-class WebSocket extends EventTarget(...WEBSOCKET_EVENTS) {
-  static CONNECTING = CONNECTING;
-  static OPEN = OPEN;
-  static CLOSING = CLOSING;
-  static CLOSED = CLOSED;
+class WebSocket extends (EventTarget(...WEBSOCKET_EVENTS): any) {
+  static CONNECTING: number = CONNECTING;
+  static OPEN: number = OPEN;
+  static CLOSING: number = CLOSING;
+  static CLOSED: number = CLOSED;
 
   CONNECTING: number = CONNECTING;
   OPEN: number = OPEN;
diff --git a/Libraries/YellowBox/UI/YellowBoxImageSource.js b/Libraries/YellowBox/UI/YellowBoxImageSource.js
index 8c186beb89e502..88822ee938e3dd 100644
--- a/Libraries/YellowBox/UI/YellowBoxImageSource.js
+++ b/Libraries/YellowBox/UI/YellowBoxImageSource.js
@@ -29,36 +29,31 @@ const scale = PixelRatio.get();
  * @license MIT
  */
 const YellowBoxImageSource = {
-  alertTriangle:
-    scale > 2
-      ? 'data:image/png;base64,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'
-      : scale > 1
-      ? 'data:image/png;base64,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'
-      : 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/9hAAAAvUlEQVQ4jbWT4Q3CIBCFP40DdANxg24gIzhKuwEjuIFxAkcwTtARGicoG+iPXlMCB8UfvoQc4e7ePV4A/ogWuMlqc0W7AsEo0QMNcPplugMmwMia5KwKWkNIuIkHq3wLXGQ/Sq4IC3wkLpOfmZyKeEpIEKsDYB8VN0Afkfpg30uNiycbdKcNqXEOxdBEWoEAoqta8uZ0iqqkxwGDUrSFAXAHZpOWd/+ubD5Kz335Cx1wZna4Bh54AddauVl8ARfCLO9Xq7xGAAAAAElFTkSuQmCC',
-  check:
-    scale > 2
-      ? 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAADAAAAAwCAYAAABXAvmHAAAAqElEQVRoge3YTQ7CIBRF4bPUu/8JS6gTSaqilh95vuR+CaO2cGgYNAUzMzOzFgHlPhRaMkDAcRoltKaTeIxPtQHxGn+Q5AgJx8cQjo8hHB9DOP76Yiu/RcTmN18WLiQCjs3zBkYXVGOeLWd+xcIr5pgyEzDz7FIjISPP/FRPUM+9W4nvYVfuCSXeB3669ldEOzRFfCUSx1cicXwlEsdXIvEPKDMzM7PMbtugw3XTpNA2AAAAAElFTkSuQmCC'
-      : scale > 1
-      ? 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACAAAAAgCAYAAABzenr0AAAAf0lEQVRYhe2UvQ2AIBQGL3EBR3AESkv3bxxFN8DmWUgwvkI+En1X0cBd+IMg+DuDyDMCs413kfMiX4EMbD3l8oCaPIU85B4mYLEF5XJscrYFPRGvb/sZ4IlocubJGdH0wj1FSG77XYT0qdUi5O+8jOjyyZQRUnkZ0UUeBMF3OQC/0VsyGlxligAAAABJRU5ErkJggg=='
-      : 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/9hAAAASElEQVQ4jWNgGJHAgIGBIYESze8ZGBjWU6L5PAMDgwBNNCdAFZJt83qoQmRDSHK2AFQhzBCy/IxsCNkBJsDAwLAfiknWPBIBAETPFeuA4fr6AAAAAElFTkSuQmCC',
-  chevronLeft:
-    scale > 2
-      ? 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAADAAAAAwCAYAAABXAvmHAAAAgElEQVRoge3YMQ6DQBAEwRYvnf8nPAECbAnkyATsrt0lXUyPdAE6kCRJ/yXA+jopLbkhwHY6a2nNl8I1ftSA8Bm/MeQKBeNrBONrBONrBONrhMHxcPwOlMUvT32oszD8CoEj+giO6CE4oofgiB7Cj44Y86zyFoYPgOFPi5Ik6WwHji+QVIOyhqgAAAAASUVORK5CYII='
-      : scale > 1
-      ? 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACQAAAAkCAYAAADhAJiYAAAAaUlEQVRYhe3WsQ2AMAwAwRcs5LEYg3HpYANoQKKgcEEUI/6adM5LbgySfmZsNDeACdiApdEfaQGswH6+Xd1jugc9xYQxxhjz9RhaxwxvDuul3MrAqDyjsozKKnWgXUqdsJcAZgqsTFJ5B7gjUNw0n0HHAAAAAElFTkSuQmCC'
-      : 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/9hAAAARklEQVQ4jWNgGPKAmUh1AQwMDBIMDAwPyLEkgYGB4T/UELI1J9BdcwCxmpnIMZ1YkECsK+hmCNZoZCHCgAUMDAwfoHg4AgDJuQ/bcLyV+QAAAABJRU5ErkJggg==',
-  chevronRight:
-    scale > 2
-      ? 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAADAAAAAwCAYAAABXAvmHAAAAeElEQVRoge3YMQ6AIBQE0Ykn3fs3HEEbC6MdFp+v8xJaspNQAZIkqbcA4zwpXTJpAPvlpHTNhHtAu4jwDDCiQjBiDcGINQQj1hCMWEN4Boy3l25vL/iL0PgJBcfXCI6vERxfIzi+Rmg8Hj7wrdL+Yys0/1qUJEmzDvSAkFQ8EOdJAAAAAElFTkSuQmCC'
-      : scale > 1
-      ? 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACQAAAAkCAYAAADhAJiYAAAAZElEQVRYhe3WsQmAQAxA0Y8ulLEcw3HtdANtBNvzCJjD/5pUgQ9pApJ+Zu7YCWABDmDLzemzA+c94+MW4AkqExUY1caoVka1GibqlSm7qJJSJzPGGGMylYqBgi9sACtFYiQN7wKC6VDcJ7tlpQAAAABJRU5ErkJggg=='
-      : 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/9hAAAANUlEQVQ4jWNgGLbAgYGBIYASAwIYGBj+MzAwJFBiSMLQMISJEpMptp2mmimORgcGChPSEAIAHGENPH8gqdYAAAAASUVORK5CYII=',
-  loader:
-    scale > 2
-      ? 'data:image/png;base64,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'
-      : scale > 1
-      ? 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACAAAAAgCAYAAABzenr0AAABN0lEQVRYhe2WzU3EMBCFP34KyJEjJaQDXAIlJJ24BSow2wEdhHSwJSwd7JHbcmC0mOxMnDiWDIInWbHkN29exo4n8IvRAEFGU8OAA04yulyR60Jm7msbyIZloAMGwBfI4UWrWxM08LW/weC4iOMNTog4g0awKjBG827GxBwC3996NHizAifsSrTRmlsZm23CT9adktyXSq6ZUPdxgiXnZzW8CLcLuC3lvqA/gCt5NtjlPQL7TP0Wu1HtRRu4PO3T4TKTz2kG+AG9IN6CR/Su9iojBw69egfghWgL/pGCp+JFVPUqTjWjlsuqeAo1o6rt2C8QcNiV0UxoHPMieojmz0CfMKyhl1hN84xbI3gnz5Ftp7kH3iT5LsFdDUf6pzSJ6r2glIFDbuDNhqRH4I7Pvv4EvG/QqocP2Jh/xzzX/zUAAAAASUVORK5CYII='
-      : 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/9hAAAAsklEQVQ4jaWTYRHCMAyFP7gJmIQ6oChgEpBQKXMwC3MADpAAEiphDuBHC4QuDRu8u9ylyWtem7Rgw2X7GT1wsghb4beAVzhtsfYyJgs44AoEQzBkjrMId1HkKPwyZ6oMSnxYsnk1NqT7yMo34Fzhd9meGJvs7Hh3NhqCLXDI/rT0lKsR+KOJgc9RdaRRarkZvELogYsi8HqxjUhGYE+aQg1jzketwFTZXHbbEpjB8eU7PwAbLiJz46707gAAAABJRU5ErkJggg==',
+  alertTriangle: ((scale > 2
+    ? 'data:image/png;base64,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'
+    : scale > 1
+    ? 'data:image/png;base64,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'
+    : 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/9hAAAAvUlEQVQ4jbWT4Q3CIBCFP40DdANxg24gIzhKuwEjuIFxAkcwTtARGicoG+iPXlMCB8UfvoQc4e7ePV4A/ogWuMlqc0W7AsEo0QMNcPplugMmwMia5KwKWkNIuIkHq3wLXGQ/Sq4IC3wkLpOfmZyKeEpIEKsDYB8VN0Afkfpg30uNiycbdKcNqXEOxdBEWoEAoqta8uZ0iqqkxwGDUrSFAXAHZpOWd/+ubD5Kz335Cx1wZna4Bh54AddauVl8ARfCLO9Xq7xGAAAAAElFTkSuQmCC'): string),
+  check: ((scale > 2
+    ? 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAADAAAAAwCAYAAABXAvmHAAAAqElEQVRoge3YTQ7CIBRF4bPUu/8JS6gTSaqilh95vuR+CaO2cGgYNAUzMzOzFgHlPhRaMkDAcRoltKaTeIxPtQHxGn+Q5AgJx8cQjo8hHB9DOP76Yiu/RcTmN18WLiQCjs3zBkYXVGOeLWd+xcIr5pgyEzDz7FIjISPP/FRPUM+9W4nvYVfuCSXeB3669ldEOzRFfCUSx1cicXwlEsdXIvEPKDMzM7PMbtugw3XTpNA2AAAAAElFTkSuQmCC'
+    : scale > 1
+    ? 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACAAAAAgCAYAAABzenr0AAAAf0lEQVRYhe2UvQ2AIBQGL3EBR3AESkv3bxxFN8DmWUgwvkI+En1X0cBd+IMg+DuDyDMCs413kfMiX4EMbD3l8oCaPIU85B4mYLEF5XJscrYFPRGvb/sZ4IlocubJGdH0wj1FSG77XYT0qdUi5O+8jOjyyZQRUnkZ0UUeBMF3OQC/0VsyGlxligAAAABJRU5ErkJggg=='
+    : 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/9hAAAASElEQVQ4jWNgGJHAgIGBIYESze8ZGBjWU6L5PAMDgwBNNCdAFZJt83qoQmRDSHK2AFQhzBCy/IxsCNkBJsDAwLAfiknWPBIBAETPFeuA4fr6AAAAAElFTkSuQmCC'): string),
+  chevronLeft: ((scale > 2
+    ? 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAADAAAAAwCAYAAABXAvmHAAAAgElEQVRoge3YMQ6DQBAEwRYvnf8nPAECbAnkyATsrt0lXUyPdAE6kCRJ/yXA+jopLbkhwHY6a2nNl8I1ftSA8Bm/MeQKBeNrBONrBONrBONrhMHxcPwOlMUvT32oszD8CoEj+giO6CE4oofgiB7Cj44Y86zyFoYPgOFPi5Ik6WwHji+QVIOyhqgAAAAASUVORK5CYII='
+    : scale > 1
+    ? 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACQAAAAkCAYAAADhAJiYAAAAaUlEQVRYhe3WsQ2AMAwAwRcs5LEYg3HpYANoQKKgcEEUI/6adM5LbgySfmZsNDeACdiApdEfaQGswH6+Xd1jugc9xYQxxhjz9RhaxwxvDuul3MrAqDyjsozKKnWgXUqdsJcAZgqsTFJ5B7gjUNw0n0HHAAAAAElFTkSuQmCC'
+    : 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/9hAAAARklEQVQ4jWNgGPKAmUh1AQwMDBIMDAwPyLEkgYGB4T/UELI1J9BdcwCxmpnIMZ1YkECsK+hmCNZoZCHCgAUMDAwfoHg4AgDJuQ/bcLyV+QAAAABJRU5ErkJggg=='): string),
+  chevronRight: ((scale > 2
+    ? 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAADAAAAAwCAYAAABXAvmHAAAAeElEQVRoge3YMQ6AIBQE0Ykn3fs3HEEbC6MdFp+v8xJaspNQAZIkqbcA4zwpXTJpAPvlpHTNhHtAu4jwDDCiQjBiDcGINQQj1hCMWEN4Boy3l25vL/iL0PgJBcfXCI6vERxfIzi+Rmg8Hj7wrdL+Yys0/1qUJEmzDvSAkFQ8EOdJAAAAAElFTkSuQmCC'
+    : scale > 1
+    ? 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACQAAAAkCAYAAADhAJiYAAAAZElEQVRYhe3WsQmAQAxA0Y8ulLEcw3HtdANtBNvzCJjD/5pUgQ9pApJ+Zu7YCWABDmDLzemzA+c94+MW4AkqExUY1caoVka1GibqlSm7qJJSJzPGGGMylYqBgi9sACtFYiQN7wKC6VDcJ7tlpQAAAABJRU5ErkJggg=='
+    : 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/9hAAAANUlEQVQ4jWNgGLbAgYGBIYASAwIYGBj+MzAwJFBiSMLQMISJEpMptp2mmimORgcGChPSEAIAHGENPH8gqdYAAAAASUVORK5CYII='): string),
+  loader: ((scale > 2
+    ? 'data:image/png;base64,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'
+    : scale > 1
+    ? 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAACAAAAAgCAYAAABzenr0AAABN0lEQVRYhe2WzU3EMBCFP34KyJEjJaQDXAIlJJ24BSow2wEdhHSwJSwd7JHbcmC0mOxMnDiWDIInWbHkN29exo4n8IvRAEFGU8OAA04yulyR60Jm7msbyIZloAMGwBfI4UWrWxM08LW/weC4iOMNTog4g0awKjBG827GxBwC3996NHizAifsSrTRmlsZm23CT9adktyXSq6ZUPdxgiXnZzW8CLcLuC3lvqA/gCt5NtjlPQL7TP0Wu1HtRRu4PO3T4TKTz2kG+AG9IN6CR/Su9iojBw69egfghWgL/pGCp+JFVPUqTjWjlsuqeAo1o6rt2C8QcNiV0UxoHPMieojmz0CfMKyhl1hN84xbI3gnz5Ftp7kH3iT5LsFdDUf6pzSJ6r2glIFDbuDNhqRH4I7Pvv4EvG/QqocP2Jh/xzzX/zUAAAAASUVORK5CYII='
+    : 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAABAAAAAQCAYAAAAf8/9hAAAAsklEQVQ4jaWTYRHCMAyFP7gJmIQ6oChgEpBQKXMwC3MADpAAEiphDuBHC4QuDRu8u9ylyWtem7Rgw2X7GT1wsghb4beAVzhtsfYyJgs44AoEQzBkjrMId1HkKPwyZ6oMSnxYsnk1NqT7yMo34Fzhd9meGJvs7Hh3NhqCLXDI/rT0lKsR+KOJgc9RdaRRarkZvELogYsi8HqxjUhGYE+aQg1jzketwFTZXHbbEpjB8eU7PwAbLiJz46707gAAAABJRU5ErkJggg=='): string),
 };
 
 module.exports = YellowBoxImageSource;
diff --git a/Libraries/YellowBox/UI/YellowBoxInspector.js b/Libraries/YellowBox/UI/YellowBoxInspector.js
index adcdc0d7333829..424b8ed5d13077 100644
--- a/Libraries/YellowBox/UI/YellowBoxInspector.js
+++ b/Libraries/YellowBox/UI/YellowBoxInspector.js
@@ -41,7 +41,7 @@ type State = {|
 class YellowBoxInspector extends React.Component<Props, State> {
   _symbolication: ?SymbolicationRequest;
 
-  state = {
+  state: State = {
     selectedIndex: 0,
   };
 
diff --git a/Libraries/YellowBox/UI/YellowBoxInspectorSourceMapStatus.js b/Libraries/YellowBox/UI/YellowBoxInspectorSourceMapStatus.js
index 48487792293959..fbd98a9ed4aa92 100644
--- a/Libraries/YellowBox/UI/YellowBoxInspectorSourceMapStatus.js
+++ b/Libraries/YellowBox/UI/YellowBoxInspectorSourceMapStatus.js
@@ -34,7 +34,7 @@ type State = {|
 |};
 
 class YellowBoxInspectorSourceMapStatus extends React.Component<Props, State> {
-  state = {
+  state: State = {
     animation: null,
     rotate: null,
   };
diff --git a/Libraries/YellowBox/UI/YellowBoxList.js b/Libraries/YellowBox/UI/YellowBoxList.js
index 2620c35852fab7..c7fa200d1d7052 100644
--- a/Libraries/YellowBox/UI/YellowBoxList.js
+++ b/Libraries/YellowBox/UI/YellowBoxList.js
@@ -11,8 +11,8 @@
 'use strict';
 
 const Dimensions = require('../../Utilities/Dimensions');
-const React = require('react');
 const FlatList = require('../../Lists/FlatList');
+const React = require('react');
 const SafeAreaView = require('../../Components/SafeAreaView/SafeAreaView');
 const StyleSheet = require('../../StyleSheet/StyleSheet');
 const View = require('../../Components/View/View');
@@ -41,7 +41,7 @@ const MAX_ITEMS = Math.floor(
 );
 
 class YellowBoxList extends React.Component<Props, State> {
-  state = {
+  state: State = {
     selectedCategory: null,
   };
 
diff --git a/Libraries/YellowBox/UI/YellowBoxListRow.js b/Libraries/YellowBox/UI/YellowBoxListRow.js
index f388c5083b117d..367a40e9c6835d 100644
--- a/Libraries/YellowBox/UI/YellowBoxListRow.js
+++ b/Libraries/YellowBox/UI/YellowBoxListRow.js
@@ -13,9 +13,9 @@
 const React = require('react');
 const StyleSheet = require('../../StyleSheet/StyleSheet');
 const Text = require('../../Text/Text');
-const YellowBoxPressable = require('./YellowBoxPressable');
 const View = require('../../Components/View/View');
 const YellowBoxCategory = require('../Data/YellowBoxCategory');
+const YellowBoxPressable = require('./YellowBoxPressable');
 const YellowBoxStyle = require('./YellowBoxStyle');
 const YellowBoxWarning = require('../Data/YellowBoxWarning');
 
@@ -28,8 +28,8 @@ type Props = $ReadOnly<{|
 |}>;
 
 class YellowBoxListRow extends React.Component<Props> {
-  static GUTTER = StyleSheet.hairlineWidth;
-  static HEIGHT = 48;
+  static GUTTER: number = StyleSheet.hairlineWidth;
+  static HEIGHT: number = 48;
 
   shouldComponentUpdate(nextProps: Props): boolean {
     const prevProps = this.props;
diff --git a/Libraries/YellowBox/UI/YellowBoxPressable.js b/Libraries/YellowBox/UI/YellowBoxPressable.js
index 0090ca69ab37f2..ed7b688a76854d 100644
--- a/Libraries/YellowBox/UI/YellowBoxPressable.js
+++ b/Libraries/YellowBox/UI/YellowBoxPressable.js
@@ -16,9 +16,9 @@ const TouchableWithoutFeedback = require('../../Components/Touchable/TouchableWi
 const View = require('../../Components/View/View');
 const YellowBoxStyle = require('./YellowBoxStyle');
 
-import type {PressEvent} from '../../Types/CoreEventTypes';
 import type {EdgeInsetsProp} from '../../StyleSheet/EdgeInsetsPropType';
 import type {ViewStyleProp} from '../../StyleSheet/StyleSheet';
+import type {PressEvent} from '../../Types/CoreEventTypes';
 
 type Props = $ReadOnly<{|
   backgroundColor: $ReadOnly<{|
@@ -36,14 +36,16 @@ type State = {|
 |};
 
 class YellowBoxPressable extends React.Component<Props, State> {
-  static defaultProps = {
+  static defaultProps: $TEMPORARY$object<{|
+    backgroundColor: $TEMPORARY$object<{|default: string, pressed: string|}>,
+  |}> = {
     backgroundColor: {
       default: YellowBoxStyle.getBackgroundColor(0.95),
       pressed: YellowBoxStyle.getHighlightColor(1),
     },
   };
 
-  state = {
+  state: State = {
     pressed: false,
   };
 
diff --git a/Libraries/vendor/emitter/EventEmitterWithHolding.js b/Libraries/vendor/emitter/EventEmitterWithHolding.js
index 945506e3c0f182..c553dde0631358 100644
--- a/Libraries/vendor/emitter/EventEmitterWithHolding.js
+++ b/Libraries/vendor/emitter/EventEmitterWithHolding.js
@@ -49,14 +49,14 @@ class EventEmitterWithHolding {
   /**
    * @see EventEmitter#addListener
    */
-  addListener(eventType: string, listener: Function, context: ?Object) {
+  addListener(eventType: string, listener: Function, context: ?Object): any {
     return this._emitter.addListener(eventType, listener, context);
   }
 
   /**
    * @see EventEmitter#once
    */
-  once(eventType: string, listener: Function, context: ?Object) {
+  once(eventType: string, listener: Function, context: ?Object): any {
     return this._emitter.once(eventType, listener, context);
   }
 
@@ -115,7 +115,7 @@ class EventEmitterWithHolding {
   /**
    * @see EventEmitter#listeners
    */
-  listeners(eventType: string) /* TODO: Annotate return type here */ {
+  listeners(eventType: string): any /* TODO: Annotate return type here */ {
     return this._emitter.listeners(eventType);
   }
 
diff --git a/Libraries/vendor/emitter/EventHolder.js b/Libraries/vendor/emitter/EventHolder.js
index ea68ef9d784848..54728e753904d1 100644
--- a/Libraries/vendor/emitter/EventHolder.js
+++ b/Libraries/vendor/emitter/EventHolder.js
@@ -42,7 +42,10 @@ class EventHolder {
    *   }); //logs 'abc'
    *
    */
-  holdEvent(eventType: string, ...args: any) {
+  holdEvent(
+    eventType: string,
+    ...args: any
+  ): $TEMPORARY$object<{|eventType: string, index: $FlowFixMeEmpty|}> {
     this._heldEvents[eventType] = this._heldEvents[eventType] || [];
     const eventsOfType = this._heldEvents[eventType];
     const key = {
diff --git a/RNTester/js/RNTesterApp.ios.js b/RNTester/js/RNTesterApp.ios.js
index 9645166d7b10ea..e7d7ab7f822165 100644
--- a/RNTester/js/RNTesterApp.ios.js
+++ b/RNTester/js/RNTesterApp.ios.js
@@ -10,7 +10,15 @@
 
 'use strict';
 
+const RNTesterActions = require('./utils/RNTesterActions');
+const RNTesterExampleContainer = require('./components/RNTesterExampleContainer');
+const RNTesterExampleList = require('./components/RNTesterExampleList');
+const RNTesterList = require('./utils/RNTesterList.ios');
+const RNTesterNavigationReducer = require('./utils/RNTesterNavigationReducer');
 const React = require('react');
+const SnapshotViewIOS = require('./examples/Snapshot/SnapshotViewIOS.ios');
+const URIActionMap = require('./utils/URIActionMap');
+
 const {
   AppRegistry,
   AsyncStorage,
@@ -23,13 +31,6 @@ const {
   View,
   YellowBox,
 } = require('react-native');
-const RNTesterActions = require('./utils/RNTesterActions');
-const RNTesterExampleContainer = require('./components/RNTesterExampleContainer');
-const RNTesterExampleList = require('./components/RNTesterExampleList');
-const RNTesterList = require('./utils/RNTesterList.ios');
-const RNTesterNavigationReducer = require('./utils/RNTesterNavigationReducer');
-const SnapshotViewIOS = require('./examples/Snapshot/SnapshotViewIOS.ios');
-const URIActionMap = require('./utils/URIActionMap');
 
 import type {RNTesterExample} from './types/RNTesterTypes';
 import type {RNTesterAction} from './utils/RNTesterActions';
@@ -109,7 +110,7 @@ class RNTesterApp extends React.Component<Props, RNTesterNavigationState> {
     }
   };
 
-  render() {
+  render(): React.Node | null {
     if (!this.state) {
       return null;
     }
diff --git a/RNTester/js/components/ListExampleShared.js b/RNTester/js/components/ListExampleShared.js
index 43e4f9424d9011..69e3ecc1510611 100644
--- a/RNTester/js/components/ListExampleShared.js
+++ b/RNTester/js/components/ListExampleShared.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {
   Animated,
   Image,
@@ -59,7 +60,7 @@ class ItemComponent extends React.PureComponent<{
   _onPress = () => {
     this.props.onPress(this.props.item.key);
   };
-  render() {
+  render(): React.Node {
     const {fixedHeight, horizontal, item} = this.props;
     const itemHash = Math.abs(hashCode(item.title));
     const imgSource = THUMB_URLS[itemHash % THUMB_URLS.length];
@@ -90,7 +91,7 @@ class ItemComponent extends React.PureComponent<{
   }
 }
 
-const renderStackedItem = ({item}: {item: Item}) => {
+const renderStackedItem = ({item}: {item: Item}): React.Node => {
   const itemHash = Math.abs(hashCode(item.title));
   const imgSource = THUMB_URLS[itemHash % THUMB_URLS.length];
   return (
@@ -104,7 +105,7 @@ const renderStackedItem = ({item}: {item: Item}) => {
 };
 
 class FooterComponent extends React.PureComponent<{}> {
-  render() {
+  render(): React.Node {
     return (
       <View style={styles.headerFooterContainer}>
         <SeparatorComponent />
@@ -117,7 +118,7 @@ class FooterComponent extends React.PureComponent<{}> {
 }
 
 class HeaderComponent extends React.PureComponent<{}> {
-  render() {
+  render(): React.Node {
     return (
       <View style={styles.headerFooterContainer}>
         <View style={styles.headerFooter}>
@@ -130,7 +131,7 @@ class HeaderComponent extends React.PureComponent<{}> {
 }
 
 class ListEmptyComponent extends React.PureComponent<{}> {
-  render() {
+  render(): React.Node {
     return (
       <View style={styles.listEmpty}>
         <Text>The list is empty :o</Text>
@@ -140,13 +141,13 @@ class ListEmptyComponent extends React.PureComponent<{}> {
 }
 
 class SeparatorComponent extends React.PureComponent<{}> {
-  render() {
+  render(): React.Node {
     return <View style={styles.separator} />;
   }
 }
 
 class ItemSeparatorComponent extends React.PureComponent<$FlowFixMeProps> {
-  render() {
+  render(): React.Node {
     const style = this.props.highlighted
       ? [
           styles.itemSeparator,
@@ -158,7 +159,7 @@ class ItemSeparatorComponent extends React.PureComponent<$FlowFixMeProps> {
 }
 
 class Spindicator extends React.PureComponent<$FlowFixMeProps> {
-  render() {
+  render(): React.Node {
     return (
       <Animated.View
         style={[
@@ -214,7 +215,11 @@ function hashCode(str: string): number {
 const HEADER = {height: 30, width: 100};
 const SEPARATOR_HEIGHT = StyleSheet.hairlineWidth;
 
-function getItemLayout(data: any, index: number, horizontal?: boolean) {
+function getItemLayout(
+  data: any,
+  index: number,
+  horizontal?: boolean,
+): $TEMPORARY$object<{|index: number, length: number, offset: number|}> {
   const [length, separator, header] = horizontal
     ? [HORIZ_WIDTH, 0, HEADER.width]
     : [ITEM_HEIGHT, SEPARATOR_HEIGHT, HEADER.height];
@@ -235,7 +240,10 @@ function pressItem(context: Object, key: string) {
   });
 }
 
-function renderSmallSwitchOption(context: Object, key: string) {
+function renderSmallSwitchOption(
+  context: Object,
+  key: string,
+): null | React.Node {
   if (Platform.isTV) {
     return null;
   }
@@ -251,7 +259,7 @@ function renderSmallSwitchOption(context: Object, key: string) {
   );
 }
 
-function PlainInput(props: Object) {
+function PlainInput(props: Object): React.Node {
   return (
     <TextInput
       autoCapitalize="none"
diff --git a/RNTester/js/components/RNTesterBlock.js b/RNTester/js/components/RNTesterBlock.js
index 6999668e6ac78b..d546de6f2481d8 100644
--- a/RNTester/js/components/RNTesterBlock.js
+++ b/RNTester/js/components/RNTesterBlock.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {StyleSheet, Text, View} = require('react-native');
 
 type Props = $ReadOnly<{|
@@ -24,9 +25,9 @@ type State = {|
 |};
 
 class RNTesterBlock extends React.Component<Props, State> {
-  state = {description: null};
+  state: State = {description: null};
 
-  render() {
+  render(): React.Node {
     const description = this.props.description ? (
       <Text style={styles.descriptionText}>{this.props.description}</Text>
     ) : null;
diff --git a/RNTester/js/components/RNTesterButton.js b/RNTester/js/components/RNTesterButton.js
index 543d52c6e0ae36..a3fa596319fab3 100644
--- a/RNTester/js/components/RNTesterButton.js
+++ b/RNTester/js/components/RNTesterButton.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {StyleSheet, Text, TouchableHighlight} = require('react-native');
 
 import type {PressEvent} from '../../../Libraries/Types/CoreEventTypes';
@@ -21,7 +22,7 @@ type Props = $ReadOnly<{|
 |}>;
 
 class RNTesterButton extends React.Component<Props> {
-  render() {
+  render(): React.Node {
     return (
       <TouchableHighlight
         onPress={this.props.onPress}
diff --git a/RNTester/js/components/RNTesterExampleFilter.js b/RNTester/js/components/RNTesterExampleFilter.js
index ba6af79bae2ce8..b16af4957fecfd 100644
--- a/RNTester/js/components/RNTesterExampleFilter.js
+++ b/RNTester/js/components/RNTesterExampleFilter.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {StyleSheet, TextInput, View} = require('react-native');
 
 type Props = {
@@ -26,9 +27,9 @@ type State = {
 };
 
 class RNTesterExampleFilter extends React.Component<Props, State> {
-  state = {filter: ''};
+  state: State = {filter: ''};
 
-  render() {
+  render(): React.Node {
     const filterText = this.state.filter;
     let filterRegex = /.*/;
 
diff --git a/RNTester/js/components/RNTesterExampleList.js b/RNTester/js/components/RNTesterExampleList.js
index c3fe40a708678e..a6cfa2c11f3b34 100644
--- a/RNTester/js/components/RNTesterExampleList.js
+++ b/RNTester/js/components/RNTesterExampleList.js
@@ -10,7 +10,10 @@
 
 'use strict';
 
+const RNTesterActions = require('../utils/RNTesterActions');
+const RNTesterExampleFilter = require('./RNTesterExampleFilter');
 const React = require('react');
+
 const {
   Platform,
   SectionList,
@@ -19,11 +22,9 @@ const {
   TouchableHighlight,
   View,
 } = require('react-native');
-const RNTesterActions = require('../utils/RNTesterActions');
-const RNTesterExampleFilter = require('./RNTesterExampleFilter');
 
-import type {RNTesterExample} from '../types/RNTesterTypes';
 import type {ViewStyleProp} from '../../../Libraries/StyleSheet/StyleSheet';
+import type {RNTesterExample} from '../types/RNTesterTypes';
 
 type Props = {
   onNavigate: Function,
@@ -69,7 +70,7 @@ const renderSectionHeader = ({section}) => (
 );
 
 class RNTesterExampleList extends React.Component<Props, $FlowFixMeState> {
-  render() {
+  render(): React.Node {
     const filter = ({example, filterRegex}) =>
       filterRegex.test(example.module.title) &&
       (!Platform.isTV || example.supportsTVOS);
diff --git a/RNTester/js/components/RNTesterPage.js b/RNTester/js/components/RNTesterPage.js
index 6b1b0fe1db6112..51481cdc8cb53f 100644
--- a/RNTester/js/components/RNTesterPage.js
+++ b/RNTester/js/components/RNTesterPage.js
@@ -10,10 +10,10 @@
 
 'use strict';
 
+const RNTesterTitle = require('./RNTesterTitle');
 const React = require('react');
-const {ScrollView, StyleSheet, View} = require('react-native');
 
-const RNTesterTitle = require('./RNTesterTitle');
+const {ScrollView, StyleSheet, View} = require('react-native');
 
 type Props = $ReadOnly<{|
   children?: React.Node,
@@ -23,7 +23,7 @@ type Props = $ReadOnly<{|
 |}>;
 
 class RNTesterPage extends React.Component<Props> {
-  render() {
+  render(): React.Node {
     let ContentWrapper;
     let wrapperProps = {};
     if (this.props.noScroll) {
diff --git a/RNTester/js/components/RNTesterTitle.js b/RNTester/js/components/RNTesterTitle.js
index a50ac5066c395e..df418fdbadcc8d 100644
--- a/RNTester/js/components/RNTesterTitle.js
+++ b/RNTester/js/components/RNTesterTitle.js
@@ -11,10 +11,11 @@
 'use strict';
 
 const React = require('react');
+
 const {StyleSheet, Text, View} = require('react-native');
 
 class RNTesterTitle extends React.Component<$FlowFixMeProps> {
-  render() {
+  render(): React.Node {
     return (
       <View style={styles.container}>
         <Text style={styles.text}>{this.props.title}</Text>
diff --git a/RNTester/js/components/TextInlineView.js b/RNTester/js/components/TextInlineView.js
index d69f5b10507833..e5fcc68aaeac4c 100644
--- a/RNTester/js/components/TextInlineView.js
+++ b/RNTester/js/components/TextInlineView.js
@@ -11,9 +11,10 @@
 'use strict';
 
 const React = require('react');
+
 const {Image, Text, TouchableHighlight, View} = require('react-native');
 
-function Basic() {
+function Basic(): React.Node {
   return (
     <Text>
       This text contains an inline blue view{' '}
@@ -24,7 +25,7 @@ function Basic() {
   );
 }
 
-function ClippedByText() {
+function ClippedByText(): React.Node {
   return (
     <View>
       {/*
@@ -92,11 +93,11 @@ type ChangeSizeState = {|
 |};
 
 class ChangeImageSize extends React.Component<*, ChangeSizeState> {
-  state = {
+  state: ChangeSizeState = {
     width: 50,
   };
 
-  render() {
+  render(): React.Node {
     return (
       <View>
         <TouchableHighlight
@@ -128,11 +129,11 @@ class ChangeImageSize extends React.Component<*, ChangeSizeState> {
 }
 
 class ChangeViewSize extends React.Component<*, ChangeSizeState> {
-  state = {
+  state: ChangeSizeState = {
     width: 50,
   };
 
-  render() {
+  render(): React.Node {
     return (
       <View>
         <TouchableHighlight
@@ -160,11 +161,11 @@ class ChangeViewSize extends React.Component<*, ChangeSizeState> {
 }
 
 class ChangeInnerViewSize extends React.Component<*, ChangeSizeState> {
-  state = {
+  state: ChangeSizeState = {
     width: 50,
   };
 
-  render() {
+  render(): React.Node {
     return (
       <View>
         <TouchableHighlight
diff --git a/RNTester/js/components/TextLegend.js b/RNTester/js/components/TextLegend.js
index 5021b8d867b874..b53bed9dd7d1df 100644
--- a/RNTester/js/components/TextLegend.js
+++ b/RNTester/js/components/TextLegend.js
@@ -11,17 +11,23 @@
 'use strict';
 
 const React = require('react');
+
 const {Picker, Text, View} = require('react-native');
 
 class TextLegend extends React.Component<*, *> {
-  state = {
+  state: $TEMPORARY$object<{|
+    alignment: $TEMPORARY$string<'left'>,
+    fontSize: number,
+    language: $TEMPORARY$string<'english'>,
+    textMetrics: Array<any>,
+  |}> = {
     textMetrics: [],
     language: 'english',
     alignment: 'left',
     fontSize: 50,
   };
 
-  render() {
+  render(): React.Node {
     const PANGRAMS = {
       arabic:
         'صِف خَلقَ خَودِ كَمِثلِ الشَمسِ إِذ بَزَغَت — يَحظى الضَجيعُ بِها نَجلاءَ مِعطارِ',
diff --git a/RNTester/js/examples/ActivityIndicator/ActivityIndicatorExample.js b/RNTester/js/examples/ActivityIndicator/ActivityIndicatorExample.js
index ca25a457aa8f18..b18ceb92934ed9 100644
--- a/RNTester/js/examples/ActivityIndicator/ActivityIndicatorExample.js
+++ b/RNTester/js/examples/ActivityIndicator/ActivityIndicatorExample.js
@@ -9,9 +9,9 @@
  */
 
 'use strict';
-
-import React, {Component} from 'react';
+import type {Node} from 'React';
 import {ActivityIndicator, StyleSheet, View} from 'react-native';
+import React, {Component} from 'react';
 
 type State = {|animating: boolean|};
 type Props = $ReadOnly<{||}>;
@@ -77,7 +77,7 @@ exports.description = 'Animated loading indicators.';
 exports.examples = [
   {
     title: 'Default (small, white)',
-    render() {
+    render(): Node {
       return (
         <ActivityIndicator
           style={[styles.centering, styles.gray]}
@@ -88,7 +88,7 @@ exports.examples = [
   },
   {
     title: 'Gray',
-    render() {
+    render(): Node {
       return (
         <View>
           <ActivityIndicator style={[styles.centering]} />
@@ -99,7 +99,7 @@ exports.examples = [
   },
   {
     title: 'Custom colors',
-    render() {
+    render(): Node {
       return (
         <View style={styles.horizontal}>
           <ActivityIndicator color="#0000ff" />
@@ -112,7 +112,7 @@ exports.examples = [
   },
   {
     title: 'Large',
-    render() {
+    render(): Node {
       return (
         <ActivityIndicator
           style={[styles.centering, styles.gray]}
@@ -124,7 +124,7 @@ exports.examples = [
   },
   {
     title: 'Large, custom colors',
-    render() {
+    render(): Node {
       return (
         <View style={styles.horizontal}>
           <ActivityIndicator size="large" color="#0000ff" />
@@ -137,13 +137,13 @@ exports.examples = [
   },
   {
     title: 'Start/stop',
-    render() {
+    render(): Node {
       return <ToggleAnimatingActivityIndicator />;
     },
   },
   {
     title: 'Custom size',
-    render() {
+    render(): Node {
       return (
         <ActivityIndicator
           style={[styles.centering, {transform: [{scale: 1.5}]}]}
@@ -155,7 +155,7 @@ exports.examples = [
   {
     platform: 'android',
     title: 'Custom size (size: 75)',
-    render() {
+    render(): Node {
       return <ActivityIndicator style={styles.centering} size={75} />;
     },
   },
diff --git a/RNTester/js/examples/Alert/AlertIOSExample.js b/RNTester/js/examples/Alert/AlertIOSExample.js
index 45c735523acb26..18bcaa4655da5a 100644
--- a/RNTester/js/examples/Alert/AlertIOSExample.js
+++ b/RNTester/js/examples/Alert/AlertIOSExample.js
@@ -11,6 +11,8 @@
 'use strict';
 
 const React = require('react');
+
+const {SimpleAlertExampleBlock} = require('./AlertExample');
 const {
   StyleSheet,
   View,
@@ -19,8 +21,6 @@ const {
   Alert,
 } = require('react-native');
 
-const {SimpleAlertExampleBlock} = require('./AlertExample');
-
 type Props = $ReadOnly<{||}>;
 type State = {|promptValue: ?string|};
 
@@ -157,7 +157,7 @@ exports.description = 'iOS alerts and action sheets';
 exports.examples = [
   {
     title: 'Alerts',
-    render() {
+    render(): React.Node {
       return <SimpleAlertExampleBlock />;
     },
   },
@@ -169,7 +169,7 @@ exports.examples = [
   },
   {
     title: 'Prompt Types',
-    render() {
+    render(): React.Node {
       return (
         <View>
           <TouchableHighlight
diff --git a/RNTester/js/examples/Animated/AnimatedExample.js b/RNTester/js/examples/Animated/AnimatedExample.js
index f11a5065a86beb..7ef971ca5ee704 100644
--- a/RNTester/js/examples/Animated/AnimatedExample.js
+++ b/RNTester/js/examples/Animated/AnimatedExample.js
@@ -10,9 +10,10 @@
 
 'use strict';
 
+const RNTesterButton = require('../../components/RNTesterButton');
 const React = require('react');
+
 const {Animated, Easing, StyleSheet, Text, View} = require('react-native');
-const RNTesterButton = require('../../components/RNTesterButton');
 
 const styles = StyleSheet.create({
   content: {
@@ -32,19 +33,17 @@ const styles = StyleSheet.create({
 
 exports.framework = 'React';
 exports.title = 'Animated - Examples';
-exports.description =
-  'Animated provides a powerful ' +
+exports.description = ('Animated provides a powerful ' +
   'and easy-to-use API for building modern, ' +
-  'interactive user experiences.';
+  'interactive user experiences.': string);
 
 exports.examples = [
   {
     title: 'FadeInView',
-    description:
-      'Uses a simple timing animation to ' +
+    description: ('Uses a simple timing animation to ' +
       'bring opacity from 0 to 1 when the component ' +
-      'mounts.',
-    render: function() {
+      'mounts.': string),
+    render: function(): React.Node {
       class FadeInView extends React.Component<$FlowFixMeProps, any> {
         constructor(props) {
           super(props);
@@ -113,13 +112,12 @@ exports.examples = [
   },
   {
     title: 'Transform Bounce',
-    description:
-      'One `Animated.Value` is driven by a ' +
+    description: ('One `Animated.Value` is driven by a ' +
       'spring with custom constants and mapped to an ' +
       'ordered set of transforms.  Each transform has ' +
       'an interpolation to convert the value into the ' +
-      'right range and units.',
-    render: function() {
+      'right range and units.': string),
+    render: function(): React.Node {
       this.anim = this.anim || new Animated.Value(0);
       return (
         <View>
@@ -181,10 +179,9 @@ exports.examples = [
   },
   {
     title: 'Composite Animations with Easing',
-    description:
-      'Sequence, parallel, delay, and ' +
-      'stagger with different easing functions.',
-    render: function() {
+    description: ('Sequence, parallel, delay, and ' +
+      'stagger with different easing functions.': string),
+    render: function(): React.Node {
       this.anims = this.anims || [1, 2, 3].map(() => new Animated.Value(0));
       return (
         <View>
@@ -279,7 +276,7 @@ exports.examples = [
   {
     title: 'Rotating Images',
     description: 'Simple Animated.Image rotation.',
-    render: function() {
+    render: function(): React.Node {
       this.anim = this.anim || new Animated.Value(0);
       return (
         <View>
@@ -340,10 +337,11 @@ exports.examples = [
   },
   {
     title: 'Continuous Interactions',
-    description:
-      'Gesture events, chaining, 2D ' +
+    description: ('Gesture events, chaining, 2D ' +
       'values, interrupting and transitioning ' +
-      'animations, etc.',
-    render: () => <Text>Checkout the Gratuitous Animation App!</Text>,
+      'animations, etc.': string),
+    render: (): React.Node => (
+      <Text>Checkout the Gratuitous Animation App!</Text>
+    ),
   },
 ];
diff --git a/RNTester/js/examples/Animated/AnimatedGratuitousApp/AnExChained.js b/RNTester/js/examples/Animated/AnimatedGratuitousApp/AnExChained.js
index f8128a629ec9c4..fb720bfe539673 100644
--- a/RNTester/js/examples/Animated/AnimatedGratuitousApp/AnExChained.js
+++ b/RNTester/js/examples/Animated/AnimatedGratuitousApp/AnExChained.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {Animated, PanResponder, StyleSheet, View} = require('react-native');
 
 class AnExChained extends React.Component<Object, any> {
@@ -68,7 +69,7 @@ class AnExChained extends React.Component<Object, any> {
     });
   }
 
-  render() {
+  render(): React.Node {
     return (
       <View style={styles.chained}>
         {this.state.stickers.map((_, i) => {
diff --git a/RNTester/js/examples/Animated/AnimatedGratuitousApp/AnExScroll.js b/RNTester/js/examples/Animated/AnimatedGratuitousApp/AnExScroll.js
index 0bd79b9635f78d..87afc77f24b2ad 100644
--- a/RNTester/js/examples/Animated/AnimatedGratuitousApp/AnExScroll.js
+++ b/RNTester/js/examples/Animated/AnimatedGratuitousApp/AnExScroll.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {
   Animated,
   Image,
@@ -23,7 +24,7 @@ const {
 class AnExScroll extends React.Component<$FlowFixMeProps, any> {
   state: any = {scrollX: new Animated.Value(0)};
 
-  render() {
+  render(): React.Node {
     const width = this.props.panelWidth;
     return (
       <View style={styles.container}>
diff --git a/RNTester/js/examples/AppState/AppStateExample.js b/RNTester/js/examples/AppState/AppStateExample.js
index 24ecbcc27450de..9e7f17eefc1201 100644
--- a/RNTester/js/examples/AppState/AppStateExample.js
+++ b/RNTester/js/examples/AppState/AppStateExample.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {AppState, Text, View} = require('react-native');
 
 class AppStateSubscription extends React.Component<
@@ -75,7 +76,7 @@ exports.examples = [
   {
     title: 'AppState.currentState',
     description: 'Can be null on app initialization',
-    render() {
+    render(): React.Node {
       return <Text>{AppState.currentState}</Text>;
     },
   },
diff --git a/RNTester/js/examples/Button/ButtonExample.js b/RNTester/js/examples/Button/ButtonExample.js
index 2dfad341b0c327..36e8a4eb4a626a 100644
--- a/RNTester/js/examples/Button/ButtonExample.js
+++ b/RNTester/js/examples/Button/ButtonExample.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {Alert, Button, View, StyleSheet} = require('react-native');
 
 function onButtonPress(buttonName) {
@@ -25,11 +26,10 @@ exports.description = 'Simple React Native button component.';
 exports.examples = [
   {
     title: 'Simple Button',
-    description:
-      'The title and onPress handler are required. It is ' +
+    description: ('The title and onPress handler are required. It is ' +
       'recommended to set accessibilityLabel to help make your app usable by ' +
-      'everyone.',
-    render: function() {
+      'everyone.': string),
+    render: function(): React.Node {
       return (
         <Button
           onPress={() => onButtonPress('Simple')}
@@ -42,11 +42,10 @@ exports.examples = [
   },
   {
     title: 'Adjusted color',
-    description:
-      'Adjusts the color in a way that looks standard on each ' +
+    description: ('Adjusts the color in a way that looks standard on each ' +
       'platform. On iOS, the color prop controls the color of the text. On ' +
-      'Android, the color adjusts the background color of the button.',
-    render: function() {
+      'Android, the color adjusts the background color of the button.': string),
+    render: function(): React.Node {
       return (
         <Button
           onPress={() => onButtonPress('Purple')}
@@ -60,9 +59,9 @@ exports.examples = [
   },
   {
     title: 'Fit to text layout',
-    description:
-      'This layout strategy lets the title define the width of ' + 'the button',
-    render: function() {
+    description: ('This layout strategy lets the title define the width of ' +
+      'the button': string),
+    render: function(): React.Node {
       return (
         <View style={styles.container}>
           <Button
@@ -85,7 +84,7 @@ exports.examples = [
   {
     title: 'Disabled Button',
     description: 'All interactions for the component are disabled.',
-    render: function() {
+    render: function(): React.Node {
       return (
         <Button
           disabled
diff --git a/RNTester/js/examples/Clipboard/ClipboardExample.js b/RNTester/js/examples/Clipboard/ClipboardExample.js
index 7bd7518b0f3c4d..791f3d7eb5e671 100644
--- a/RNTester/js/examples/Clipboard/ClipboardExample.js
+++ b/RNTester/js/examples/Clipboard/ClipboardExample.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {Clipboard, View, Text, StyleSheet} = require('react-native');
 
 type Props = $ReadOnly<{||}>;
@@ -60,7 +61,7 @@ exports.description = 'Show Clipboard contents.';
 exports.examples = [
   {
     title: 'Clipboard.setString() and getString()',
-    render() {
+    render(): React.Node {
       return <ClipboardExample />;
     },
   },
diff --git a/RNTester/js/examples/Crash/CrashExample.js b/RNTester/js/examples/Crash/CrashExample.js
index 6b28592355b99f..1232137de3e646 100644
--- a/RNTester/js/examples/Crash/CrashExample.js
+++ b/RNTester/js/examples/Crash/CrashExample.js
@@ -9,9 +9,9 @@
  */
 
 'use strict';
-
-import React from 'react';
+import type {Node} from 'React';
 import {NativeModules, Button} from 'react-native';
+import React from 'react';
 
 const {CrashyCrash} = NativeModules;
 
@@ -23,7 +23,7 @@ exports.description = 'Crash examples.';
 exports.examples = [
   {
     title: 'JS crash',
-    render() {
+    render(): Node {
       return (
         <Button
           title="JS crash"
@@ -38,7 +38,7 @@ exports.examples = [
   },
   {
     title: 'Native crash',
-    render() {
+    render(): Node {
       return (
         <Button
           title="Native crash"
diff --git a/RNTester/js/examples/Dimensions/DimensionsExample.js b/RNTester/js/examples/Dimensions/DimensionsExample.js
index 6ba52411f05bfe..c593cec95ecbdd 100644
--- a/RNTester/js/examples/Dimensions/DimensionsExample.js
+++ b/RNTester/js/examples/Dimensions/DimensionsExample.js
@@ -10,8 +10,8 @@
 
 'use strict';
 
-import * as React from 'react';
 import {Dimensions, Text, useWindowDimensions} from 'react-native';
+import * as React from 'react';
 
 class DimensionsSubscription extends React.Component<
   {dim: string},
@@ -45,7 +45,7 @@ exports.description = 'Dimensions of the viewport';
 exports.examples = [
   {
     title: 'useWindowDimensions hook',
-    render() {
+    render(): React.Node {
       const DimensionsViaHook = () => {
         const dims = useWindowDimensions();
         return <Text>{JSON.stringify(dims, null, 2)}</Text>;
diff --git a/RNTester/js/examples/FlatList/FlatListExample.js b/RNTester/js/examples/FlatList/FlatListExample.js
index 9a14a8951233c2..bb7cc9afe88c02 100644
--- a/RNTester/js/examples/FlatList/FlatListExample.js
+++ b/RNTester/js/examples/FlatList/FlatListExample.js
@@ -10,12 +10,8 @@
 
 'use strict';
 
-import type {Item} from '../../components/ListExampleShared';
-
-const React = require('react');
-const {Alert, Animated, StyleSheet, View} = require('react-native');
-
 const RNTesterPage = require('../../components/RNTesterPage');
+const React = require('react');
 
 const infoLog = require('../../../../Libraries/Utilities/infoLog');
 
@@ -33,6 +29,9 @@ const {
   pressItem,
   renderSmallSwitchOption,
 } = require('../../components/ListExampleShared');
+const {Alert, Animated, StyleSheet, View} = require('react-native');
+
+import type {Item} from '../../components/ListExampleShared';
 
 const VIEWABILITY_CONFIG = {
   minimumViewTime: 3000,
@@ -55,7 +54,7 @@ type State = {|
 |};
 
 class FlatListExample extends React.PureComponent<Props, State> {
-  state = {
+  state: State = {
     data: genItemData(100),
     debug: false,
     horizontal: false,
@@ -92,7 +91,7 @@ class FlatListExample extends React.PureComponent<Props, State> {
     this._listRef.getNode().recordInteraction(); // e.g. flipping logViewable switch
   }
 
-  render() {
+  render(): React.Node {
     const filterRegex = new RegExp(String(this.state.filterText), 'i');
     const filter = item =>
       filterRegex.test(item.text) || filterRegex.test(item.title);
diff --git a/RNTester/js/examples/Image/ImageCapInsetsExample.js b/RNTester/js/examples/Image/ImageCapInsetsExample.js
index 4524e99c5e8c96..a7ab1de9349fe7 100644
--- a/RNTester/js/examples/Image/ImageCapInsetsExample.js
+++ b/RNTester/js/examples/Image/ImageCapInsetsExample.js
@@ -18,7 +18,7 @@ const {Image, StyleSheet, Text, View} = ReactNative;
 
 type Props = $ReadOnly<{||}>;
 class ImageCapInsetsExample extends React.Component<Props> {
-  render() {
+  render(): React.Node {
     return (
       <View>
         <View style={styles.background}>
diff --git a/RNTester/js/examples/Image/ImageExample.js b/RNTester/js/examples/Image/ImageExample.js
index c3aaa8418ffb7e..3fd95a4594f9b0 100644
--- a/RNTester/js/examples/Image/ImageExample.js
+++ b/RNTester/js/examples/Image/ImageExample.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {
   ActivityIndicator,
   Image,
@@ -408,19 +409,17 @@ exports.description =
 exports.examples = [
   {
     title: 'Plain Network Image',
-    description:
-      'If the `source` prop `uri` property is prefixed with ' +
-      '"http", then it will be downloaded from the network.',
-    render: function() {
+    description: ('If the `source` prop `uri` property is prefixed with ' +
+      '"http", then it will be downloaded from the network.': string),
+    render: function(): React.Node {
       return <Image source={fullImage} style={styles.base} />;
     },
   },
   {
     title: 'Plain Static Image',
-    description:
-      'Static assets should be placed in the source code tree, and ' +
-      'required in the same way as JavaScript modules.',
-    render: function() {
+    description: ('Static assets should be placed in the source code tree, and ' +
+      'required in the same way as JavaScript modules.': string),
+    render: function(): React.Node {
       return (
         <View style={styles.horizontal}>
           <Image
@@ -445,7 +444,7 @@ exports.examples = [
   },
   {
     title: 'Image Loading Events',
-    render: function() {
+    render: function(): React.Node {
       return (
         <NetworkImageCallbackExample
           source={{
@@ -460,7 +459,7 @@ exports.examples = [
   },
   {
     title: 'Error Handler',
-    render: function() {
+    render: function(): React.Node {
       return (
         <NetworkImageExample
           source={{
@@ -473,7 +472,7 @@ exports.examples = [
   },
   {
     title: 'Image Download Progress',
-    render: function() {
+    render: function(): React.Node {
       return (
         <NetworkImageExample
           source={{
@@ -487,7 +486,7 @@ exports.examples = [
   {
     title: 'defaultSource',
     description: 'Show a placeholder image when a network image is loading',
-    render: function() {
+    render: function(): React.Node {
       return (
         <Image
           defaultSource={require('../../assets/bunny.png')}
@@ -502,11 +501,10 @@ exports.examples = [
   },
   {
     title: 'Cache Policy',
-    description:
-      'First image has never been loaded before and is instructed not to load unless in cache.' +
+    description: ('First image has never been loaded before and is instructed not to load unless in cache.' +
       'Placeholder image from above will stay. Second image is the same but forced to load regardless of' +
-      ' local cache state.',
-    render: function() {
+      ' local cache state.': string),
+    render: function(): React.Node {
       return (
         <View style={styles.horizontal}>
           <Image
@@ -532,7 +530,7 @@ exports.examples = [
   },
   {
     title: 'Border Color',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View style={styles.horizontal}>
           <Image
@@ -549,7 +547,7 @@ exports.examples = [
   },
   {
     title: 'Border Width',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View style={styles.horizontal}>
           <Image
@@ -566,7 +564,7 @@ exports.examples = [
   },
   {
     title: 'Border Radius',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View style={styles.horizontal}>
           <Image style={[styles.base, {borderRadius: 5}]} source={fullImage} />
@@ -612,7 +610,7 @@ exports.examples = [
   },
   {
     title: 'Background Color',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View style={styles.horizontal}>
           <Image source={smallImage} style={styles.base} />
@@ -638,7 +636,7 @@ exports.examples = [
   },
   {
     title: 'Opacity',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View style={styles.horizontal}>
           <Image style={[styles.base, {opacity: 1}]} source={fullImage} />
@@ -668,7 +666,7 @@ exports.examples = [
   },
   {
     title: 'Nesting content inside <Image> component',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View style={{width: 60, height: 60}}>
           <Image
@@ -682,7 +680,7 @@ exports.examples = [
   },
   {
     title: 'Nesting content inside <ImageBackground> component',
-    render: function() {
+    render: function(): React.Node {
       return (
         <ImageBackground
           style={{width: 60, height: 60, backgroundColor: 'transparent'}}
@@ -694,10 +692,9 @@ exports.examples = [
   },
   {
     title: 'Tint Color',
-    description:
-      'The `tintColor` style prop changes all the non-alpha ' +
-      'pixels to the tint color.',
-    render: function() {
+    description: ('The `tintColor` style prop changes all the non-alpha ' +
+      'pixels to the tint color.': string),
+    render: function(): React.Node {
       return (
         <View>
           <View style={styles.horizontal}>
@@ -769,10 +766,9 @@ exports.examples = [
   },
   {
     title: 'Resize Mode',
-    description:
-      'The `resizeMode` style prop controls how the image is ' +
-      'rendered within the frame.',
-    render: function() {
+    description: ('The `resizeMode` style prop controls how the image is ' +
+      'rendered within the frame.': string),
+    render: function(): React.Node {
       return (
         <View>
           {[smallImage, fullImage].map((image, index) => {
@@ -831,7 +827,7 @@ exports.examples = [
   },
   {
     title: 'Animated GIF',
-    render: function() {
+    render: function(): React.Node {
       return (
         <Image
           style={styles.gif}
@@ -843,7 +839,7 @@ exports.examples = [
   },
   {
     title: 'Base64 image',
-    render: function() {
+    render: function(): React.Node {
       return (
         <Image style={styles.base64} source={{uri: base64Icon, scale: 3}} />
       );
@@ -852,44 +848,41 @@ exports.examples = [
   },
   {
     title: 'Cap Insets',
-    description:
-      'When the image is resized, the corners of the size specified ' +
+    description: ('When the image is resized, the corners of the size specified ' +
       'by capInsets will stay a fixed size, but the center content and ' +
       'borders of the image will be stretched. This is useful for creating ' +
-      'resizable rounded buttons, shadows, and other resizable assets.',
-    render: function() {
+      'resizable rounded buttons, shadows, and other resizable assets.': string),
+    render: function(): React.Node {
       return <ImageCapInsetsExample />;
     },
     platform: 'ios',
   },
   {
     title: 'Image Size',
-    render: function() {
+    render: function(): React.Node {
       return <ImageSizeExample source={fullImage} />;
     },
   },
   {
     title: 'MultipleSourcesExample',
-    description:
-      'The `source` prop allows passing in an array of uris, so that native to choose which image ' +
-      'to diplay based on the size of the of the target image',
-    render: function() {
+    description: ('The `source` prop allows passing in an array of uris, so that native to choose which image ' +
+      'to diplay based on the size of the of the target image': string),
+    render: function(): React.Node {
       return <MultipleSourcesExample />;
     },
   },
   {
     title: 'Legacy local image',
-    description:
-      'Images shipped with the native bundle, but not managed ' +
-      'by the JS packager',
-    render: function() {
+    description: ('Images shipped with the native bundle, but not managed ' +
+      'by the JS packager': string),
+    render: function(): React.Node {
       return <Image source={{uri: 'legacy_image', width: 120, height: 120}} />;
     },
   },
   {
     title: 'Bundled images',
     description: 'Images shipped in a separate native bundle',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View style={{flexDirection: 'row'}}>
           <Image
@@ -917,7 +910,7 @@ exports.examples = [
   },
   {
     title: 'Blur Radius',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View style={styles.horizontal}>
           <Image style={[styles.base]} source={fullImage} blurRadius={0} />
diff --git a/RNTester/js/examples/JSResponderHandlerExample/JSResponderHandlerExample.js b/RNTester/js/examples/JSResponderHandlerExample/JSResponderHandlerExample.js
index a7507598731c27..de7a78aaf782dc 100644
--- a/RNTester/js/examples/JSResponderHandlerExample/JSResponderHandlerExample.js
+++ b/RNTester/js/examples/JSResponderHandlerExample/JSResponderHandlerExample.js
@@ -11,7 +11,9 @@
 'use strict';
 
 const React = require('react');
+
 const {Text, View, StyleSheet} = require('react-native');
+
 import {PanResponder, ScrollView} from 'react-native';
 
 exports.displayName = 'JSResponderHandlerExample';
@@ -28,13 +30,12 @@ const _gesture = PanResponder.create({
 exports.examples = [
   {
     title: 'JSResponderHandlerExample',
-    description:
-      'This example tests the native JSResponderHandler: when the user ' +
+    description: ('This example tests the native JSResponderHandler: when the user ' +
       'scrolls on the right side of the ScrollView (white area located on the' +
       ' right side of the gray area), the touch event is managed by native ' +
-      'which blocks the scroll event.',
+      'which blocks the scroll event.': string),
 
-    render: function() {
+    render: function(): React.Node {
       const views = [];
       for (let i = 0; i < 100; i++) {
         views[i] = (
diff --git a/RNTester/js/examples/Layout/LayoutEventsExample.js b/RNTester/js/examples/Layout/LayoutEventsExample.js
index b556c272d17f51..000b52dafc1572 100644
--- a/RNTester/js/examples/Layout/LayoutEventsExample.js
+++ b/RNTester/js/examples/Layout/LayoutEventsExample.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {
   Image,
   LayoutAnimation,
@@ -152,9 +153,8 @@ const styles = StyleSheet.create({
 });
 
 exports.title = 'Layout Events';
-exports.description =
-  'Examples that show how Layout events can be used to ' +
-  'measure view size and position.';
+exports.description = ('Examples that show how Layout events can be used to ' +
+  'measure view size and position.': string);
 exports.examples = [
   {
     title: 'LayoutEventExample',
diff --git a/RNTester/js/examples/Layout/LayoutExample.js b/RNTester/js/examples/Layout/LayoutExample.js
index 1d2050effcbe6c..9c69038f30f76f 100644
--- a/RNTester/js/examples/Layout/LayoutExample.js
+++ b/RNTester/js/examples/Layout/LayoutExample.js
@@ -10,11 +10,11 @@
 
 'use strict';
 
-const React = require('react');
-const {StyleSheet, Text, View} = require('react-native');
-
 const RNTesterBlock = require('../../components/RNTesterBlock');
 const RNTesterPage = require('../../components/RNTesterPage');
+const React = require('react');
+
+const {StyleSheet, Text, View} = require('react-native');
 
 class Circle extends React.Component<$FlowFixMeProps> {
   render() {
@@ -50,7 +50,7 @@ class CircleBlock extends React.Component<$FlowFixMeProps> {
 }
 
 class LayoutExample extends React.Component<$FlowFixMeProps> {
-  render() {
+  render(): React.Node {
     const fiveColoredCircles = [
       <Circle bgColor="#527fe4" key="blue" />,
       <Circle bgColor="#D443E3" key="violet" />,
diff --git a/RNTester/js/examples/MaskedView/MaskedViewExample.js b/RNTester/js/examples/MaskedView/MaskedViewExample.js
index 22dd6e1aaa5802..2b9f99c19a0aa6 100644
--- a/RNTester/js/examples/MaskedView/MaskedViewExample.js
+++ b/RNTester/js/examples/MaskedView/MaskedViewExample.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {
   Animated,
   Image,
@@ -54,7 +55,7 @@ class AnimatedMaskExample extends React.Component<Props> {
     ).start();
   }
 
-  render() {
+  render(): React.Node {
     return (
       <View style={styles.exampleWrapperStyle}>
         <MaskedViewIOS
@@ -93,7 +94,7 @@ class ChangingChildrenMaskExample extends React.Component<
   Props,
   ChangingChildrenState,
 > {
-  state = {
+  state: ChangingChildrenState = {
     alternateChildren: true,
   };
 
@@ -105,7 +106,7 @@ class ChangingChildrenMaskExample extends React.Component<
     }, 1000);
   }
 
-  render() {
+  render(): React.Node {
     return (
       <View style={styles.exampleWrapperStyle}>
         <MaskedViewIOS
diff --git a/RNTester/js/examples/Modal/ModalExample.js b/RNTester/js/examples/Modal/ModalExample.js
index 2defd129a267d6..2279df565e6249 100644
--- a/RNTester/js/examples/Modal/ModalExample.js
+++ b/RNTester/js/examples/Modal/ModalExample.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {
   Modal,
   Picker,
@@ -236,7 +237,7 @@ exports.examples = [
   {
     title: 'Modal Presentation',
     description: 'Modals can be presented with or without animation',
-    render: () => <ModalExample />,
+    render: (): React.Node => <ModalExample />,
   },
 ];
 
diff --git a/RNTester/js/examples/MultiColumn/MultiColumnExample.js b/RNTester/js/examples/MultiColumn/MultiColumnExample.js
index f79ea22a0697ae..480090d1b1a502 100644
--- a/RNTester/js/examples/MultiColumn/MultiColumnExample.js
+++ b/RNTester/js/examples/MultiColumn/MultiColumnExample.js
@@ -9,11 +9,8 @@
  */
 
 'use strict';
-
-const React = require('react');
-const {FlatList, StyleSheet, Text, View, Alert} = require('react-native');
-
 const RNTesterPage = require('../../components/RNTesterPage');
+const React = require('react');
 
 const infoLog = require('../../../../Libraries/Utilities/infoLog');
 
@@ -28,12 +25,24 @@ const {
   pressItem,
   renderSmallSwitchOption,
 } = require('../../components/ListExampleShared');
+const {FlatList, StyleSheet, Text, View, Alert} = require('react-native');
+
+import type {Item} from '../../components/ListExampleShared';
 
 class MultiColumnExample extends React.PureComponent<
   $FlowFixMeProps,
   $FlowFixMeState,
 > {
-  state = {
+  state:
+    | any
+    | $TEMPORARY$object<{|
+        data: Array<Item>,
+        filterText: string,
+        fixedHeight: boolean,
+        logViewable: boolean,
+        numColumns: number,
+        virtualized: boolean,
+      |}> = {
     data: genItemData(1000),
     filterText: '',
     fixedHeight: true,
@@ -47,7 +56,7 @@ class MultiColumnExample extends React.PureComponent<
   _onChangeNumColumns = numColumns => {
     this.setState(() => ({numColumns: Number(numColumns)}));
   };
-  render() {
+  render(): React.Node {
     const filterRegex = new RegExp(String(this.state.filterText), 'i');
     const filter = item =>
       filterRegex.test(item.text) || filterRegex.test(item.title);
diff --git a/RNTester/js/examples/NativeAnimation/NativeAnimationsExample.js b/RNTester/js/examples/NativeAnimation/NativeAnimationsExample.js
index acec03baa04dfa..f654aa4ca9760d 100644
--- a/RNTester/js/examples/NativeAnimation/NativeAnimationsExample.js
+++ b/RNTester/js/examples/NativeAnimation/NativeAnimationsExample.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {
   View,
   Text,
@@ -371,7 +372,7 @@ exports.description = 'Test out Native Animations';
 exports.examples = [
   {
     title: 'Multistage With Multiply and rotation',
-    render: function() {
+    render: function(): React.Node {
       return (
         <Tester type="timing" config={{duration: 1000}}>
           {anim => (
@@ -419,7 +420,7 @@ exports.examples = [
   },
   {
     title: 'Multistage With Multiply',
-    render: function() {
+    render: function(): React.Node {
       return (
         <Tester type="timing" config={{duration: 1000}}>
           {anim => (
@@ -461,7 +462,7 @@ exports.examples = [
   },
   {
     title: 'Multistage With Subtract',
-    render: function() {
+    render: function(): React.Node {
       return (
         <Tester type="timing" config={{duration: 1000}}>
           {anim => (
@@ -503,7 +504,7 @@ exports.examples = [
   },
   {
     title: 'Scale interpolation with clamping',
-    render: function() {
+    render: function(): React.Node {
       return (
         <Tester type="timing" config={{duration: 1000}}>
           {anim => (
@@ -530,7 +531,7 @@ exports.examples = [
   },
   {
     title: 'Opacity with delay',
-    render: function() {
+    render: function(): React.Node {
       return (
         <Tester type="timing" config={{duration: 1000, delay: 1000}}>
           {anim => (
@@ -549,7 +550,7 @@ exports.examples = [
   },
   {
     title: 'Rotate interpolation',
-    render: function() {
+    render: function(): React.Node {
       return (
         <Tester type="timing" config={{duration: 1000}}>
           {anim => (
@@ -575,7 +576,7 @@ exports.examples = [
   },
   {
     title: 'translateX => Animated.spring (bounciness/speed)',
-    render: function() {
+    render: function(): React.Node {
       return (
         <Tester type="spring" config={{bounciness: 0}}>
           {anim => (
@@ -601,7 +602,7 @@ exports.examples = [
   },
   {
     title: 'translateX => Animated.spring (stiffness/damping/mass)',
-    render: function() {
+    render: function(): React.Node {
       return (
         <Tester type="spring" config={{stiffness: 1000, damping: 500, mass: 3}}>
           {anim => (
@@ -627,7 +628,7 @@ exports.examples = [
   },
   {
     title: 'translateX => Animated.decay',
-    render: function() {
+    render: function(): React.Node {
       return (
         <Tester
           type="decay"
@@ -653,7 +654,7 @@ exports.examples = [
   },
   {
     title: 'Drive custom property (tap to animate)',
-    render: function() {
+    render: function(): React.Node {
       return (
         <Tester type="timing" config={{duration: 1000}}>
           {anim => <AnimatedSlider style={{}} value={anim} />}
@@ -663,31 +664,31 @@ exports.examples = [
   },
   {
     title: 'Animated value listener',
-    render: function() {
+    render: function(): React.Node {
       return <ValueListenerExample />;
     },
   },
   {
     title: 'Animated loop',
-    render: function() {
+    render: function(): React.Node {
       return <LoopExample />;
     },
   },
   {
     title: 'Animated events',
-    render: function() {
+    render: function(): React.Node {
       return <EventExample />;
     },
   },
   {
     title: 'Animated Tracking - tap me many times',
-    render: function() {
+    render: function(): React.Node {
       return <TrackingExample />;
     },
   },
   {
     title: 'Internal Settings',
-    render: function() {
+    render: function(): React.Node {
       return <InternalSettings />;
     },
   },
diff --git a/RNTester/js/examples/OrientationChange/OrientationChangeExample.js b/RNTester/js/examples/OrientationChange/OrientationChangeExample.js
index 509ab84b0dc598..5375a68fd77120 100644
--- a/RNTester/js/examples/OrientationChange/OrientationChangeExample.js
+++ b/RNTester/js/examples/OrientationChange/OrientationChangeExample.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {DeviceEventEmitter, Text, View} = require('react-native');
 
 import type EmitterSubscription from '../../../../Libraries/vendor/emitter/EmitterSubscription';
@@ -58,7 +59,7 @@ exports.examples = [
   {
     title: 'OrientationChangeExample',
     description: 'listening to device orientation changes',
-    render() {
+    render(): React.Node {
       return <OrientationChangeExample />;
     },
   },
diff --git a/RNTester/js/examples/PermissionsAndroid/PermissionsExample.js b/RNTester/js/examples/PermissionsAndroid/PermissionsExample.js
index afc065146ee703..3e7b2f2b41bd41 100644
--- a/RNTester/js/examples/PermissionsAndroid/PermissionsExample.js
+++ b/RNTester/js/examples/PermissionsAndroid/PermissionsExample.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {
   PermissionsAndroid,
   Picker,
@@ -108,7 +109,7 @@ exports.examples = [
     title: 'Permissions Example',
     description:
       'Short example of how to use the runtime permissions API introduced in Android M.',
-    render: () => <PermissionsExample />,
+    render: (): React.Node => <PermissionsExample />,
   },
 ];
 
diff --git a/RNTester/js/examples/Picker/PickerExample.js b/RNTester/js/examples/Picker/PickerExample.js
index b9af4bb67e2f3a..d43a7dd3cdfe60 100644
--- a/RNTester/js/examples/Picker/PickerExample.js
+++ b/RNTester/js/examples/Picker/PickerExample.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {Picker, StyleSheet, Text} = require('react-native');
 
 const Item = Picker.Item;
@@ -20,11 +21,11 @@ type State = {
 };
 
 class BasicPickerExample extends React.Component<{}, State> {
-  state = {
+  state: State = {
     value: 'key1',
   };
 
-  render() {
+  render(): React.Node {
     return (
       <Picker
         testID="basic-picker"
@@ -39,11 +40,11 @@ class BasicPickerExample extends React.Component<{}, State> {
 }
 
 class DisabledPickerExample extends React.Component<{}, State> {
-  state = {
+  state: State = {
     value: 'key1',
   };
 
-  render() {
+  render(): React.Node {
     return (
       <Picker
         style={styles.picker}
@@ -57,11 +58,11 @@ class DisabledPickerExample extends React.Component<{}, State> {
 }
 
 class DropdownPickerExample extends React.Component<{}, State> {
-  state = {
+  state: State = {
     value: 'key1',
   };
 
-  render() {
+  render(): React.Node {
     return (
       <Picker
         style={styles.picker}
@@ -76,11 +77,11 @@ class DropdownPickerExample extends React.Component<{}, State> {
 }
 
 class PromptPickerExample extends React.Component<{}, State> {
-  state = {
+  state: State = {
     value: 'key1',
   };
 
-  render() {
+  render(): React.Node {
     return (
       <Picker
         style={styles.picker}
@@ -99,11 +100,11 @@ type ColorState = {
 };
 
 class ColorPickerExample extends React.Component<{}, ColorState> {
-  state = {
+  state: ColorState = {
     color: 'red',
   };
 
-  render() {
+  render(): React.Node {
     return (
       <>
         <Picker
diff --git a/RNTester/js/examples/PointerEvents/PointerEventsExample.js b/RNTester/js/examples/PointerEvents/PointerEventsExample.js
index f3726683890b3a..fc033b04881bc4 100644
--- a/RNTester/js/examples/PointerEvents/PointerEventsExample.js
+++ b/RNTester/js/examples/PointerEvents/PointerEventsExample.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {StyleSheet, Text, View} = require('react-native');
 
 class ExampleBox extends React.Component<$FlowFixMeProps, $FlowFixMeState> {
@@ -233,10 +234,9 @@ const styles = StyleSheet.create({
 
 exports.framework = 'React';
 exports.title = 'Pointer Events';
-exports.description =
-  'Demonstrates the use of the pointerEvents prop of a ' +
-  'View to control how touches should be handled.';
+exports.description = ('Demonstrates the use of the pointerEvents prop of a ' +
+  'View to control how touches should be handled.': string);
 /* $FlowFixMe(>=0.70.0 site=react_native_fb) This comment suppresses an error
  * found when Flow v0.70 was deployed. To see the error delete this comment
  * and run Flow. */
-exports.examples = exampleClasses.map(infoToExample);
+exports.examples = (exampleClasses.map(infoToExample): Array<any>);
diff --git a/RNTester/js/examples/ProgressViewIOS/ProgressViewIOSExample.js b/RNTester/js/examples/ProgressViewIOS/ProgressViewIOSExample.js
index c9968ba4c257e5..e2c729cfbfd166 100644
--- a/RNTester/js/examples/ProgressViewIOS/ProgressViewIOSExample.js
+++ b/RNTester/js/examples/ProgressViewIOS/ProgressViewIOSExample.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {ProgressViewIOS, StyleSheet, View} = require('react-native');
 
 type Props = {||};
@@ -98,7 +99,7 @@ exports.description = 'ProgressViewIOS';
 exports.examples = [
   {
     title: 'ProgressViewIOS',
-    render() {
+    render(): React.Node {
       return <ProgressViewExample />;
     },
   },
diff --git a/RNTester/js/examples/RTL/RTLExample.js b/RNTester/js/examples/RTL/RTLExample.js
index fe26776e526642..ae44f88352dd51 100644
--- a/RNTester/js/examples/RTL/RTLExample.js
+++ b/RNTester/js/examples/RTL/RTLExample.js
@@ -10,6 +10,7 @@
 'use strict';
 
 const React = require('react');
+
 const {
   Alert,
   Animated,
@@ -657,18 +658,16 @@ exports.examples = [
   },
   {
     title: 'Default Text Alignment',
-    description:
-      'In iOS, it depends on active language. ' +
-      'In Android, it depends on the text content.',
+    description: ('In iOS, it depends on active language. ' +
+      'In Android, it depends on the text content.': string),
     render: function(): React.Element<any> {
       return <TextAlignmentExample style={styles.fontSizeSmall} />;
     },
   },
   {
     title: "Using textAlign: 'left'",
-    description:
-      'In iOS/Android, text alignment flips regardless of ' +
-      'languages or text content.',
+    description: ('In iOS/Android, text alignment flips regardless of ' +
+      'languages or text content.': string),
     render: function(): React.Element<any> {
       return (
         <TextAlignmentExample
@@ -679,9 +678,8 @@ exports.examples = [
   },
   {
     title: "Using textAlign: 'right'",
-    description:
-      'In iOS/Android, text alignment flips regardless of ' +
-      'languages or text content.',
+    description: ('In iOS/Android, text alignment flips regardless of ' +
+      'languages or text content.': string),
     render: function(): React.Element<any> {
       return (
         <TextAlignmentExample
diff --git a/RNTester/js/examples/RootViewSizeFlexibilityExample/RootViewSizeFlexibilityExampleApp.js b/RNTester/js/examples/RootViewSizeFlexibilityExample/RootViewSizeFlexibilityExampleApp.js
index 0ae1066a4cd7e9..acd4f52733a24a 100644
--- a/RNTester/js/examples/RootViewSizeFlexibilityExample/RootViewSizeFlexibilityExampleApp.js
+++ b/RNTester/js/examples/RootViewSizeFlexibilityExample/RootViewSizeFlexibilityExampleApp.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {StyleSheet, Text, TouchableHighlight, View} = require('react-native');
 
 class RootViewSizeFlexibilityExampleApp extends React.Component<
@@ -26,7 +27,7 @@ class RootViewSizeFlexibilityExampleApp extends React.Component<
     this.setState({toggled: !this.state.toggled});
   }
 
-  render() {
+  render(): React.Node {
     const viewStyle = this.state.toggled
       ? styles.bigContainer
       : styles.smallContainer;
diff --git a/RNTester/js/examples/SafeAreaView/SafeAreaViewExample.js b/RNTester/js/examples/SafeAreaView/SafeAreaViewExample.js
index d92acd76f19c03..638e678b9679b1 100644
--- a/RNTester/js/examples/SafeAreaView/SafeAreaViewExample.js
+++ b/RNTester/js/examples/SafeAreaView/SafeAreaViewExample.js
@@ -10,6 +10,7 @@
 'use strict';
 
 const React = require('react');
+
 const {
   Button,
   DeviceInfo,
@@ -122,15 +123,14 @@ exports.examples = [
     title: '<SafeAreaView> Example',
     description:
       'SafeAreaView automatically applies paddings reflect the portion of the view that is not covered by other (special) ancestor views.',
-    render: () => <SafeAreaViewExample />,
+    render: (): React.Node => <SafeAreaViewExample />,
   },
   {
     title: 'isIPhoneX_deprecated Example',
-    description:
-      '`DeviceInfo.isIPhoneX_deprecated` returns true only on iPhone X. ' +
+    description: ('`DeviceInfo.isIPhoneX_deprecated` returns true only on iPhone X. ' +
       'Note: This prop is deprecated and will be removed in a future ' +
       'release. Please use this only for a quick and temporary solution. ' +
-      'Use <SafeAreaView> instead.',
-    render: () => <IsIPhoneXExample />,
+      'Use <SafeAreaView> instead.': string),
+    render: (): React.Node => <IsIPhoneXExample />,
   },
 ];
diff --git a/RNTester/js/examples/ScrollView/ScrollViewAnimatedExample.js b/RNTester/js/examples/ScrollView/ScrollViewAnimatedExample.js
index d69e91ded20659..a111dad80afbdb 100644
--- a/RNTester/js/examples/ScrollView/ScrollViewAnimatedExample.js
+++ b/RNTester/js/examples/ScrollView/ScrollViewAnimatedExample.js
@@ -26,7 +26,7 @@ const {
 class ScrollViewAnimatedExample extends Component<{}> {
   _scrollViewPos = new Animated.Value(0);
 
-  startAnimation = () => {
+  startAnimation: () => void = () => {
     this._scrollViewPos.setValue(0);
     Animated.timing(this._scrollViewPos, {
       toValue: 100,
@@ -36,7 +36,7 @@ class ScrollViewAnimatedExample extends Component<{}> {
     }).start();
   };
 
-  render() {
+  render(): React.Node {
     const interpolated = this._scrollViewPos.interpolate({
       inputRange: [0, 1],
       outputRange: [0, 0.1],
diff --git a/RNTester/js/examples/ScrollView/ScrollViewExample.js b/RNTester/js/examples/ScrollView/ScrollViewExample.js
index 8b975df5172211..55a5c0767e9ff3 100644
--- a/RNTester/js/examples/ScrollView/ScrollViewExample.js
+++ b/RNTester/js/examples/ScrollView/ScrollViewExample.js
@@ -10,6 +10,7 @@
 'use strict';
 
 const React = require('react');
+
 const {
   Platform,
   ScrollView,
@@ -30,7 +31,7 @@ exports.examples = [
     title: '<ScrollView>\n',
     description:
       'To make content scrollable, wrap it within a <ScrollView> component',
-    render: function() {
+    render: function(): React.Node {
       let _scrollView: ScrollView;
       return (
         <View>
@@ -73,7 +74,7 @@ exports.examples = [
     title: '<ScrollView> (horizontal = true)\n',
     description:
       "You can display <ScrollView>'s child components horizontally rather than vertically",
-    render: function() {
+    render: function(): React.Node {
       function renderScrollView(
         title: string,
         additionalStyles: ViewStyleProp,
@@ -127,7 +128,7 @@ exports.examples = [
   {
     title: '<ScrollView> enable & disable\n',
     description: 'ScrollView scrolling behaviour can be disabled and enabled',
-    render: function() {
+    render: function(): React.Node {
       class EnableDisableList extends React.Component<{}, *> {
         state = {
           scrollEnabled: true,
diff --git a/RNTester/js/examples/ScrollView/ScrollViewSimpleExample.js b/RNTester/js/examples/ScrollView/ScrollViewSimpleExample.js
index 1cbf4834543743..5487fa866cca69 100644
--- a/RNTester/js/examples/ScrollView/ScrollViewSimpleExample.js
+++ b/RNTester/js/examples/ScrollView/ScrollViewSimpleExample.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {
   ScrollView,
   StyleSheet,
@@ -24,7 +25,10 @@ class ScrollViewSimpleExample extends React.Component<{}> {
   /* $FlowFixMe(>=0.98.0 site=react_native_fb) This comment suppresses an error
    * found when Flow v0.98 was deployed. To see the error delete this comment
    * and run Flow. */
-  makeItems = (nItems: number, styles): Array<any> => {
+  makeItems: (nItems: number, styles: any) => Array<any> = (
+    nItems: number,
+    styles,
+  ): Array<any> => {
     const items = [];
     for (let i = 0; i < nItems; i++) {
       items[i] = (
@@ -36,7 +40,7 @@ class ScrollViewSimpleExample extends React.Component<{}> {
     return items;
   };
 
-  render() {
+  render(): React.Node {
     // One of the items is a horizontal scroll view
     const items = this.makeItems(NUM_ITEMS, styles.itemWrapper);
     items[4] = (
diff --git a/RNTester/js/examples/SectionList/SectionListExample.js b/RNTester/js/examples/SectionList/SectionListExample.js
index 76e131f5c97640..014fa48a0b14b9 100644
--- a/RNTester/js/examples/SectionList/SectionListExample.js
+++ b/RNTester/js/examples/SectionList/SectionListExample.js
@@ -9,18 +9,8 @@
  */
 
 'use strict';
-
-const React = require('react');
-const {
-  Alert,
-  Animated,
-  Button,
-  StyleSheet,
-  Text,
-  View,
-} = require('react-native');
-
 const RNTesterPage = require('../../components/RNTesterPage');
+const React = require('react');
 
 const infoLog = require('../../../../Libraries/Utilities/infoLog');
 
@@ -36,6 +26,16 @@ const {
   renderSmallSwitchOption,
   renderStackedItem,
 } = require('../../components/ListExampleShared');
+const {
+  Alert,
+  Animated,
+  Button,
+  StyleSheet,
+  Text,
+  View,
+} = require('react-native');
+
+import type {Item} from '../../components/ListExampleShared';
 
 const VIEWABILITY_CONFIG = {
   minimumViewTime: 3000,
@@ -68,7 +68,16 @@ const CustomSeparatorComponent = ({highlighted, text}) => (
 );
 
 class SectionListExample extends React.PureComponent<{}, $FlowFixMeState> {
-  state = {
+  state:
+    | any
+    | $TEMPORARY$object<{|
+        data: Array<Item>,
+        debug: boolean,
+        filterText: string,
+        inverted: boolean,
+        logViewable: boolean,
+        virtualized: boolean,
+      |}> = {
     data: genItemData(1000),
     debug: false,
     filterText: '',
@@ -92,7 +101,7 @@ class SectionListExample extends React.PureComponent<{}, $FlowFixMeState> {
     this._sectionListRef.getNode().scrollToLocation({sectionIndex, itemIndex});
   }
 
-  render() {
+  render(): React.Node {
     const filterRegex = new RegExp(String(this.state.filterText), 'i');
     const filter = item =>
       filterRegex.test(item.text) || filterRegex.test(item.title);
diff --git a/RNTester/js/examples/SetPropertiesExample/SetPropertiesExampleApp.js b/RNTester/js/examples/SetPropertiesExample/SetPropertiesExampleApp.js
index 7ec83f58bdfb9b..7021943ddccdbc 100644
--- a/RNTester/js/examples/SetPropertiesExample/SetPropertiesExampleApp.js
+++ b/RNTester/js/examples/SetPropertiesExample/SetPropertiesExampleApp.js
@@ -11,10 +11,11 @@
 'use strict';
 
 const React = require('react');
+
 const {Text, View} = require('react-native');
 
 class SetPropertiesExampleApp extends React.Component<$FlowFixMeProps> {
-  render() {
+  render(): React.Node {
     const wrapperStyle = {
       backgroundColor: this.props.color,
       flex: 1,
diff --git a/RNTester/js/examples/Share/ShareExample.js b/RNTester/js/examples/Share/ShareExample.js
index 489031d2a2e5ea..0d4bf3b6f0a0c1 100644
--- a/RNTester/js/examples/Share/ShareExample.js
+++ b/RNTester/js/examples/Share/ShareExample.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {
   StyleSheet,
   View,
@@ -119,7 +120,7 @@ exports.description = 'Share data with other Apps.';
 exports.examples = [
   {
     title: 'Share Text Content',
-    render() {
+    render(): React.Node {
       return <ShareMessageExample />;
     },
   },
diff --git a/RNTester/js/examples/StatusBar/StatusBarExample.js b/RNTester/js/examples/StatusBar/StatusBarExample.js
index 09972b3c92d9ca..3180dc24911617 100644
--- a/RNTester/js/examples/StatusBar/StatusBarExample.js
+++ b/RNTester/js/examples/StatusBar/StatusBarExample.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {
   StatusBar,
   StyleSheet,
@@ -433,55 +434,55 @@ exports.description = 'Component for controlling the status bar';
 exports.examples = [
   {
     title: 'StatusBar hidden',
-    render() {
+    render(): React.Node {
       return <StatusBarHiddenExample />;
     },
   },
   {
     title: 'StatusBar style',
-    render() {
+    render(): React.Node {
       return <StatusBarStyleExample />;
     },
     platform: 'ios',
   },
   {
     title: 'StatusBar network activity indicator',
-    render() {
+    render(): React.Node {
       return <StatusBarNetworkActivityExample />;
     },
     platform: 'ios',
   },
   {
     title: 'StatusBar background color',
-    render() {
+    render(): React.Node {
       return <StatusBarBackgroundColorExample />;
     },
     platform: 'android',
   },
   {
     title: 'StatusBar translucent',
-    render() {
+    render(): React.Node {
       return <StatusBarTranslucentExample />;
     },
     platform: 'android',
   },
   {
     title: 'StatusBar static API',
-    render() {
+    render(): React.Node {
       return <StatusBarStaticIOSExample />;
     },
     platform: 'ios',
   },
   {
     title: 'StatusBar static API',
-    render() {
+    render(): React.Node {
       return <StatusBarStaticAndroidExample />;
     },
     platform: 'android',
   },
   {
     title: 'StatusBar dimensions',
-    render() {
+    render(): React.Node {
       return (
         <View>
           <Text>Height (Android only): {StatusBar.currentHeight} pts</Text>
diff --git a/RNTester/js/examples/TVEventHandler/TVEventHandlerExample.js b/RNTester/js/examples/TVEventHandler/TVEventHandlerExample.js
index 82f2f41755ba14..2980bc12745e08 100644
--- a/RNTester/js/examples/TVEventHandler/TVEventHandlerExample.js
+++ b/RNTester/js/examples/TVEventHandler/TVEventHandlerExample.js
@@ -81,7 +81,7 @@ exports.description = 'iOS alerts and action sheets';
 exports.examples = [
   {
     title: 'TVEventHandler',
-    render() {
+    render(): React.Node {
       return <TVEventHandlerView />;
     },
   },
diff --git a/RNTester/js/examples/Text/TextExample.ios.js b/RNTester/js/examples/Text/TextExample.ios.js
index 5835161d1fa83c..8b28c6dfb26756 100644
--- a/RNTester/js/examples/Text/TextExample.ios.js
+++ b/RNTester/js/examples/Text/TextExample.ios.js
@@ -11,6 +11,10 @@
 'use strict';
 
 const React = require('react');
+const TextAncestor = require('../../../../Libraries/Text/TextAncestor');
+const TextInlineView = require('../../components/TextInlineView');
+const TextLegend = require('../../components/TextLegend');
+
 const {
   Button,
   LayoutAnimation,
@@ -19,9 +23,6 @@ const {
   TextInput,
   View,
 } = require('react-native');
-const TextAncestor = require('../../../../Libraries/Text/TextAncestor');
-const TextInlineView = require('../../components/TextInlineView');
-const TextLegend = require('../../components/TextLegend');
 
 // TODO: Is there a cleaner way to flip the TextAncestor value to false? I
 //   suspect apps won't even be able to leverage this workaround because
@@ -459,7 +460,7 @@ exports.displayName = 'TextExample';
 exports.examples = [
   {
     title: 'Wrap',
-    render: function() {
+    render: function(): React.Node {
       return (
         <Text>
           The text should wrap if it goes on multiple lines. See, this is going
@@ -470,13 +471,13 @@ exports.examples = [
   },
   {
     title: "Substring Emoji (should only see 'test')",
-    render: function() {
+    render: function(): React.Node {
       return <Text>{'test🙃'.substring(0, 5)}</Text>;
     },
   },
   {
     title: 'Transparent Background Color',
-    render: function() {
+    render: function(): React.Node {
       return (
         <Text style={{backgroundColor: '#00000020', padding: 10}}>
           Text in a gray box!
@@ -489,17 +490,17 @@ exports.examples = [
   },
   {
     title: 'Text metrics',
-    render: function() {
+    render: function(): React.Node {
       return <TextRenderInfoExample />;
     },
   },
   {
     title: 'Text metrics legend',
-    render: () => <TextLegend />,
+    render: (): React.Node => <TextLegend />,
   },
   {
     title: 'Baseline capheight box',
-    render: () => (
+    render: (): React.Node => (
       <View style={{backgroundColor: 'red'}}>
         <TextWithCapBaseBox>Some example text.</TextWithCapBaseBox>
       </View>
@@ -507,7 +508,7 @@ exports.examples = [
   },
   {
     title: 'Padding',
-    render: function() {
+    render: function(): React.Node {
       return (
         <Text style={{padding: 10}}>
           This text is indented by 10px padding on all sides.
@@ -517,7 +518,7 @@ exports.examples = [
   },
   {
     title: 'Font Family',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <Text style={{fontFamily: Platform.isTV ? 'Times' : 'Cochin'}}>
@@ -550,7 +551,7 @@ exports.examples = [
   },
   {
     title: 'Font Size',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <Text style={{fontSize: 23}}>Size 23</Text>
@@ -561,7 +562,7 @@ exports.examples = [
   },
   {
     title: 'Color',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <Text style={{color: 'red'}}>Red color</Text>
@@ -572,7 +573,7 @@ exports.examples = [
   },
   {
     title: 'Font Weight',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <Text style={{fontSize: 20, fontWeight: '100'}}>
@@ -596,7 +597,7 @@ exports.examples = [
   },
   {
     title: 'Font Style',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <Text style={{fontStyle: 'normal'}}>Normal text</Text>
@@ -607,7 +608,7 @@ exports.examples = [
   },
   {
     title: 'Selectable',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <Text selectable={true}>
@@ -620,7 +621,7 @@ exports.examples = [
   },
   {
     title: 'Text Decoration',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <Text
@@ -695,11 +696,10 @@ exports.examples = [
   },
   {
     title: 'Nested',
-    description:
-      'Nested text components will inherit the styles of their ' +
+    description: ('Nested text components will inherit the styles of their ' +
       'parents (only backgroundColor is inherited from non-Text parents).  ' +
-      '<Text> only supports other <Text> and raw text (strings) as children.',
-    render: function() {
+      '<Text> only supports other <Text> and raw text (strings) as children.': string),
+    render: function(): React.Node {
       return (
         <View>
           <Text>
@@ -737,7 +737,7 @@ exports.examples = [
   },
   {
     title: 'Text Align',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <Text>auto (default) - english LTR</Text>
@@ -769,7 +769,7 @@ exports.examples = [
   },
   {
     title: 'Letter Spacing',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <Text style={{letterSpacing: 0}}>letterSpacing = 0</Text>
@@ -813,7 +813,7 @@ exports.examples = [
   },
   {
     title: 'Spaces',
-    render: function() {
+    render: function(): React.Node {
       return (
         <Text>
           A {'generated'} {'string'} and some &nbsp;&nbsp;&nbsp; spaces
@@ -823,7 +823,7 @@ exports.examples = [
   },
   {
     title: 'Line Height',
-    render: function() {
+    render: function(): React.Node {
       return (
         <Text>
           <Text style={{lineHeight: 35}}>
@@ -837,7 +837,7 @@ exports.examples = [
   {
     title: 'Empty Text',
     description: "It's ok to have Text with zero or null children.",
-    render: function() {
+    render: function(): React.Node {
       return <Text />;
     },
   },
@@ -850,7 +850,7 @@ exports.examples = [
   {
     title: 'backgroundColor attribute',
     description: 'backgroundColor is inherited from all types of views.',
-    render: function() {
+    render: function(): React.Node {
       return (
         <Text style={{backgroundColor: 'yellow'}}>
           Yellow container background,
@@ -876,7 +876,7 @@ exports.examples = [
   },
   {
     title: 'numberOfLines attribute',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <Text numberOfLines={1}>
@@ -897,7 +897,7 @@ exports.examples = [
   },
   {
     title: 'Text highlighting (tap the link to see highlight)',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <Text>
@@ -923,7 +923,7 @@ exports.examples = [
   },
   {
     title: 'allowFontScaling attribute',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <Text>
@@ -951,27 +951,27 @@ exports.examples = [
   },
   {
     title: 'Inline views',
-    render: () => <TextInlineView.Basic />,
+    render: (): React.Node => <TextInlineView.Basic />,
   },
   {
     title: 'Inline image/view clipped by <Text>',
-    render: () => <TextInlineView.ClippedByText />,
+    render: (): React.Node => <TextInlineView.ClippedByText />,
   },
   {
     title: 'Relayout inline image',
-    render: () => <TextInlineView.ChangeImageSize />,
+    render: (): React.Node => <TextInlineView.ChangeImageSize />,
   },
   {
     title: 'Relayout inline view',
-    render: () => <TextInlineView.ChangeViewSize />,
+    render: (): React.Node => <TextInlineView.ChangeViewSize />,
   },
   {
     title: 'Relayout nested inline view',
-    render: () => <TextInlineView.ChangeInnerViewSize />,
+    render: (): React.Node => <TextInlineView.ChangeInnerViewSize />,
   },
   {
     title: 'Text shadow',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <Text
@@ -989,7 +989,7 @@ exports.examples = [
   },
   {
     title: 'Ellipsize mode',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <Text numberOfLines={1}>
@@ -1010,7 +1010,7 @@ exports.examples = [
   },
   {
     title: 'Font variants',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <Text style={{fontVariant: ['small-caps']}}>Small Caps{'\n'}</Text>
@@ -1044,7 +1044,7 @@ exports.examples = [
   },
   {
     title: 'Nested content',
-    render: function() {
+    render: function(): React.Node {
       // iOS-only because it relies on inline views being able to size to content.
       // Android's implementation requires that a width and height be specified
       // on the inline view.
@@ -1078,19 +1078,19 @@ exports.examples = [
   },
   {
     title: 'Text Align with RTL',
-    render: function() {
+    render: function(): React.Node {
       return <TextAlignRTLExample />;
     },
   },
   {
     title: "Text `alignItems: 'baseline'` style",
-    render: function() {
+    render: function(): React.Node {
       return <TextBaseLineLayoutExample />;
     },
   },
   {
     title: 'Transform',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <Text style={{textTransform: 'uppercase'}}>
diff --git a/RNTester/js/examples/TextInput/TextInputExample.ios.js b/RNTester/js/examples/TextInput/TextInputExample.ios.js
index a3aea1a754f578..f21ca72d32c30b 100644
--- a/RNTester/js/examples/TextInput/TextInputExample.ios.js
+++ b/RNTester/js/examples/TextInput/TextInputExample.ios.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {
   Button,
   InputAccessoryView,
@@ -592,7 +593,7 @@ exports.description = 'Single and multi-line text inputs.';
 exports.examples = [
   {
     title: 'Auto-focus',
-    render: function() {
+    render: function(): React.Node {
       return (
         <TextInput
           autoFocus={true}
@@ -604,31 +605,31 @@ exports.examples = [
   },
   {
     title: "Live Re-Write (<sp>  ->  '_') + maxLength",
-    render: function() {
+    render: function(): React.Node {
       return <RewriteExample />;
     },
   },
   {
     title: 'Live Re-Write (no spaces allowed)',
-    render: function() {
+    render: function(): React.Node {
       return <RewriteExampleInvalidCharacters />;
     },
   },
   {
     title: 'Live Re-Write (ひ -> 日)',
-    render: function() {
+    render: function(): React.Node {
       return <RewriteExampleKana />;
     },
   },
   {
     title: 'Keyboard Accessory View',
-    render: function() {
+    render: function(): React.Node {
       return <TextInputAccessoryViewExample />;
     },
   },
   {
     title: 'Auto-capitalize',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <WithLabel label="none">
@@ -649,7 +650,7 @@ exports.examples = [
   },
   {
     title: 'Auto-correct',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <WithLabel label="true">
@@ -664,7 +665,7 @@ exports.examples = [
   },
   {
     title: 'Nested content and `value` property',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <WithLabel label="singleline">
@@ -690,7 +691,7 @@ exports.examples = [
   },
   {
     title: 'Keyboard types',
-    render: function() {
+    render: function(): React.Node {
       const keyboardTypes = [
         'default',
         'ascii-capable',
@@ -717,7 +718,7 @@ exports.examples = [
   },
   {
     title: 'Keyboard appearance',
-    render: function() {
+    render: function(): React.Node {
       const keyboardAppearance = ['default', 'light', 'dark'];
       const examples = keyboardAppearance.map(type => {
         return (
@@ -731,7 +732,7 @@ exports.examples = [
   },
   {
     title: 'Return key types',
-    render: function() {
+    render: function(): React.Node {
       const returnKeyTypes = [
         'default',
         'go',
@@ -757,7 +758,7 @@ exports.examples = [
   },
   {
     title: 'Enable return key automatically',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <WithLabel label="true">
@@ -772,7 +773,7 @@ exports.examples = [
   },
   {
     title: 'Secure text entry',
-    render: function() {
+    render: function(): React.Node {
       return <SecureEntryExample />;
     },
   },
@@ -784,7 +785,7 @@ exports.examples = [
   },
   {
     title: 'Colored input text',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <TextInput
@@ -801,7 +802,7 @@ exports.examples = [
   },
   {
     title: 'Colored highlight/cursor for text input',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <TextInput
@@ -820,7 +821,7 @@ exports.examples = [
   },
   {
     title: 'Clear button mode',
-    render: function() {
+    render: function(): React.Node {
       const clearButtonModes = [
         'never',
         'while-editing',
@@ -843,7 +844,7 @@ exports.examples = [
   },
   {
     title: 'Clear and select',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <WithLabel label="clearTextOnFocus">
@@ -892,7 +893,7 @@ exports.examples = [
   },
   {
     title: 'Multiline blur on submit',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <TextInput
@@ -911,7 +912,7 @@ exports.examples = [
   },
   {
     title: 'Multiline',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <TextInput
@@ -954,7 +955,7 @@ exports.examples = [
   },
   {
     title: 'TextInput Intrinsic Size',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <Text>Singleline TextInput</Text>
@@ -1021,7 +1022,7 @@ exports.examples = [
   },
   {
     title: 'Auto-expanding',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <TextInput
@@ -1038,7 +1039,7 @@ exports.examples = [
   },
   {
     title: 'Auto-expanding',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <AutogrowingTextInputExample
@@ -1069,13 +1070,13 @@ exports.examples = [
   },
   {
     title: 'Attributed text',
-    render: function() {
+    render: function(): React.Node {
       return <TokenizedTextExample />;
     },
   },
   {
     title: 'Text selection & cursor placement',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <SelectionExample
@@ -1093,7 +1094,7 @@ exports.examples = [
   },
   {
     title: 'TextInput maxLength',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <WithLabel label="maxLength: 5">
@@ -1126,7 +1127,7 @@ exports.examples = [
   },
   {
     title: 'Text Content Type',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <WithLabel label="emailAddress">
@@ -1141,7 +1142,7 @@ exports.examples = [
   },
   {
     title: 'TextInput Placeholder Styles',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <WithLabel label="letterSpacing: 10 lineHeight: 20 textAlign: 'center'">
diff --git a/RNTester/js/examples/Timer/TimerExample.js b/RNTester/js/examples/Timer/TimerExample.js
index b0a0ce8223f20c..de13ae9f845f92 100644
--- a/RNTester/js/examples/Timer/TimerExample.js
+++ b/RNTester/js/examples/Timer/TimerExample.js
@@ -10,11 +10,13 @@
 
 'use strict';
 
-const React = require('react');
-const {Alert, Platform, ToastAndroid, Text, View} = require('react-native');
 const RNTesterButton = require('../../components/RNTesterButton');
+const React = require('react');
+
 const performanceNow = require('fbjs/lib/performanceNow');
 
+const {Alert, Platform, ToastAndroid, Text, View} = require('react-native');
+
 function burnCPU(milliseconds) {
   const start = performanceNow();
   while (performanceNow() < start + milliseconds) {}
@@ -267,11 +269,10 @@ exports.description = 'A demonstration of Timers in React Native.';
 exports.examples = [
   {
     title: 'this.setTimeout(fn, t)',
-    description:
-      'Execute function fn t milliseconds in the future.  If ' +
+    description: ('Execute function fn t milliseconds in the future.  If ' +
       't === 0, it will be enqueued immediately in the next event loop.  ' +
-      'Larger values will fire on the closest frame.',
-    render: function() {
+      'Larger values will fire on the closest frame.': string),
+    render: function(): React.Node {
       return (
         <View>
           <TimerTester type="setTimeout" dt={0} />
@@ -284,7 +285,7 @@ exports.examples = [
   {
     title: 'this.requestAnimationFrame(fn)',
     description: 'Execute function fn on the next frame.',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <TimerTester type="requestAnimationFrame" />
@@ -295,7 +296,7 @@ exports.examples = [
   {
     title: 'this.requestIdleCallback(fn)',
     description: 'Execute function fn on the next JS frame that has idle time',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <RequestIdleCallbackTester />
@@ -306,7 +307,7 @@ exports.examples = [
   {
     title: 'this.setImmediate(fn)',
     description: 'Execute function fn at the end of the current JS event loop.',
-    render: function() {
+    render: function(): React.Node {
       return (
         <View>
           <TimerTester type="setImmediate" />
@@ -316,10 +317,9 @@ exports.examples = [
   },
   {
     title: 'this.setInterval(fn, t)',
-    description:
-      'Execute function fn every t milliseconds until cancelled ' +
-      'or component is unmounted.',
-    render: function() {
+    description: ('Execute function fn every t milliseconds until cancelled ' +
+      'or component is unmounted.': string),
+    render: function(): React.Node {
       type IntervalExampleProps = $ReadOnly<{||}>;
       type IntervalExampleState = {|
         showTimer: boolean,
diff --git a/RNTester/js/examples/Touchable/TouchableExample.js b/RNTester/js/examples/Touchable/TouchableExample.js
index c1767e444180e1..8049e74d1dc0eb 100644
--- a/RNTester/js/examples/Touchable/TouchableExample.js
+++ b/RNTester/js/examples/Touchable/TouchableExample.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {
   Animated,
   Image,
@@ -470,29 +471,27 @@ exports.title = '<Touchable*> and onPress';
 exports.examples = [
   {
     title: '<TouchableHighlight>',
-    description:
-      'TouchableHighlight works by adding an extra view with a ' +
+    description: ('TouchableHighlight works by adding an extra view with a ' +
       'black background under the single child view.  This works best when the ' +
       'child view is fully opaque, although it can be made to work as a simple ' +
       'background color change as well with the activeOpacity and ' +
-      'underlayColor props.',
-    render: function() {
+      'underlayColor props.': string),
+    render: function(): React.Node {
       return <TouchableHighlightBox />;
     },
   },
   {
     title: '<TouchableWithoutFeedback>',
-    render: function() {
+    render: function(): React.Node {
       return <TouchableWithoutFeedbackBox />;
     },
   },
   {
     title: 'TouchableNativeFeedback with Animated child',
-    description:
-      'TouchableNativeFeedback can have an AnimatedComponent as a' +
-      'direct child.',
+    description: ('TouchableNativeFeedback can have an AnimatedComponent as a' +
+      'direct child.': string),
     platform: 'android',
-    render: function() {
+    render: function(): React.Node {
       const mScale = new Animated.Value(1);
       Animated.timing(mScale, {
         toValue: 0.3,
@@ -524,19 +523,17 @@ exports.examples = [
   },
   {
     title: 'Touchable feedback events',
-    description:
-      '<Touchable*> components accept onPress, onPressIn, ' +
-      'onPressOut, and onLongPress as props.',
+    description: ('<Touchable*> components accept onPress, onPressIn, ' +
+      'onPressOut, and onLongPress as props.': string),
     render: function(): React.Element<any> {
       return <TouchableFeedbackEvents />;
     },
   },
   {
     title: 'Touchable delay for events',
-    description:
-      '<Touchable*> components also accept delayPressIn, ' +
+    description: ('<Touchable*> components also accept delayPressIn, ' +
       'delayPressOut, and delayLongPress as props. These props impact the ' +
-      'timing of feedback events.',
+      'timing of feedback events.': string),
     render: function(): React.Element<any> {
       return <TouchableDelayEvents />;
     },
@@ -552,18 +549,16 @@ exports.examples = [
   },
   {
     title: 'Touchable Hit Slop',
-    description:
-      '<Touchable*> components accept hitSlop prop which extends the touch area ' +
-      'without changing the view bounds.',
+    description: ('<Touchable*> components accept hitSlop prop which extends the touch area ' +
+      'without changing the view bounds.': string),
     render: function(): React.Element<any> {
       return <TouchableHitSlop />;
     },
   },
   {
     title: 'Disabled Touchable*',
-    description:
-      '<Touchable*> components accept disabled prop which prevents ' +
-      'any interaction with component',
+    description: ('<Touchable*> components accept disabled prop which prevents ' +
+      'any interaction with component': string),
     render: function(): React.Element<any> {
       return <TouchableDisabled />;
     },
diff --git a/RNTester/js/examples/Transform/TransformExample.js b/RNTester/js/examples/Transform/TransformExample.js
index 031f7e5cbebce5..1fe09ebcff157c 100644
--- a/RNTester/js/examples/Transform/TransformExample.js
+++ b/RNTester/js/examples/Transform/TransformExample.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {Animated, StyleSheet, Text, View} = require('react-native');
 
 class Flip extends React.Component<{}, $FlowFixMeState> {
@@ -203,7 +204,7 @@ exports.examples = [
     title: 'Translate, Rotate, Scale',
     description:
       "translateX: 100, translateY: 50, rotate: '30deg', scaleX: 2, scaleY: 2",
-    render() {
+    render(): React.Node {
       return (
         <View style={styles.container}>
           <View style={styles.box1} />
@@ -215,7 +216,7 @@ exports.examples = [
     title: 'Scale, Translate, Rotate, ',
     description:
       "scaleX: 2, scaleY: 2, translateX: 100, translateY: 50, rotate: '30deg'",
-    render() {
+    render(): React.Node {
       return (
         <View style={styles.container}>
           <View style={styles.box2} />
@@ -226,7 +227,7 @@ exports.examples = [
   {
     title: 'Rotate',
     description: "rotate: '30deg'",
-    render() {
+    render(): React.Node {
       return (
         <View style={styles.container}>
           <View style={styles.box3step1} />
@@ -237,7 +238,7 @@ exports.examples = [
   {
     title: 'Rotate, Scale',
     description: "rotate: '30deg', scaleX: 2, scaleY: 2",
-    render() {
+    render(): React.Node {
       return (
         <View style={styles.container}>
           <View style={styles.box3step2} />
@@ -249,7 +250,7 @@ exports.examples = [
     title: 'Rotate, Scale, Translate ',
     description:
       "rotate: '30deg', scaleX: 2, scaleY: 2, translateX: 100, translateY: 50",
-    render() {
+    render(): React.Node {
       return (
         <View style={styles.container}>
           <View style={styles.box3step3} />
@@ -260,7 +261,7 @@ exports.examples = [
   {
     title: 'Translate, Scale, Rotate',
     description: "translate: [200, 350], scale: 2.5, rotate: '-0.2rad'",
-    render() {
+    render(): React.Node {
       return (
         <View style={styles.container}>
           <View style={styles.box4} />
@@ -271,7 +272,7 @@ exports.examples = [
   {
     title: 'Translate, Rotate, Scale',
     description: "translate: [-50, 35], rotate: '50deg', scale: 2",
-    render() {
+    render(): React.Node {
       return (
         <View style={styles.container}>
           <View style={[styles.box5, styles.box5Transform]} />
diff --git a/RNTester/js/examples/Vibration/VibrationExample.js b/RNTester/js/examples/Vibration/VibrationExample.js
index a40b3de9e2f152..b328d80f538db8 100644
--- a/RNTester/js/examples/Vibration/VibrationExample.js
+++ b/RNTester/js/examples/Vibration/VibrationExample.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {
   StyleSheet,
   View,
@@ -48,7 +49,7 @@ subsequent args: duration to wait before next vibration.
 exports.examples = [
   {
     title: 'Pattern Descriptions',
-    render() {
+    render(): React.Node {
       return (
         <View style={styles.wrapper}>
           <Text>{patternDescription}</Text>
@@ -58,7 +59,7 @@ exports.examples = [
   },
   {
     title: 'Vibration.vibrate()',
-    render() {
+    render(): React.Node {
       return (
         <TouchableHighlight
           style={styles.wrapper}
@@ -72,7 +73,7 @@ exports.examples = [
   },
   {
     title: `Vibration.vibrate(${patternLiteral})`,
-    render() {
+    render(): React.Node {
       return (
         <TouchableHighlight
           style={styles.wrapper}
@@ -86,7 +87,7 @@ exports.examples = [
   },
   {
     title: `Vibration.vibrate(${patternLiteral}, true)`,
-    render() {
+    render(): React.Node {
       return (
         <TouchableHighlight
           style={styles.wrapper}
@@ -100,7 +101,7 @@ exports.examples = [
   },
   {
     title: 'Vibration.cancel()',
-    render() {
+    render(): React.Node {
       return (
         <TouchableHighlight
           style={styles.wrapper}
diff --git a/RNTester/js/examples/View/ViewExample.js b/RNTester/js/examples/View/ViewExample.js
index 6c27499cce81ff..06b27412120e4e 100644
--- a/RNTester/js/examples/View/ViewExample.js
+++ b/RNTester/js/examples/View/ViewExample.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {
   StyleSheet,
   Text,
@@ -19,15 +20,14 @@ const {
 } = require('react-native');
 
 exports.title = '<View>';
-exports.description =
-  'Basic building block of all UI, examples that ' +
-  'demonstrate some of the many styles available.';
+exports.description = ('Basic building block of all UI, examples that ' +
+  'demonstrate some of the many styles available.': string);
 
 exports.displayName = 'ViewExample';
 exports.examples = [
   {
     title: 'Background Color',
-    render() {
+    render(): React.Node {
       return (
         <View style={{backgroundColor: '#527FE4', padding: 5}}>
           <Text style={{fontSize: 11}}>Blue background</Text>
@@ -37,7 +37,7 @@ exports.examples = [
   },
   {
     title: 'Border',
-    render() {
+    render(): React.Node {
       return (
         <View style={{borderColor: '#527FE4', borderWidth: 5, padding: 10}}>
           <Text style={{fontSize: 11}}>5px blue border</Text>
@@ -47,7 +47,7 @@ exports.examples = [
   },
   {
     title: 'Padding/Margin',
-    render() {
+    render(): React.Node {
       const styles = StyleSheet.create({
         box: {
           backgroundColor: '#527FE4',
@@ -77,7 +77,7 @@ exports.examples = [
   },
   {
     title: 'Border Radius',
-    render() {
+    render(): React.Node {
       return (
         <View style={{borderWidth: 0.5, borderRadius: 5, padding: 5}}>
           <Text style={{fontSize: 11}}>
@@ -90,7 +90,7 @@ exports.examples = [
   },
   {
     title: 'Border Style',
-    render() {
+    render(): React.Node {
       type Props = $ReadOnly<{||}>;
       type State = {|
         showBorder: boolean,
@@ -149,7 +149,7 @@ exports.examples = [
   },
   {
     title: 'Circle with Border Radius',
-    render() {
+    render(): React.Node {
       return (
         <View
           style={{borderRadius: 10, borderWidth: 1, width: 20, height: 20}}
@@ -159,7 +159,7 @@ exports.examples = [
   },
   {
     title: 'Overflow',
-    render() {
+    render(): React.Node {
       const styles = StyleSheet.create({
         container: {
           borderWidth: StyleSheet.hairlineWidth,
@@ -199,7 +199,7 @@ exports.examples = [
   },
   {
     title: 'Opacity',
-    render() {
+    render(): React.Node {
       return (
         <View>
           <View style={{opacity: 0}}>
@@ -229,7 +229,7 @@ exports.examples = [
   },
   {
     title: 'Offscreen Alpha Compositing',
-    render() {
+    render(): React.Node {
       type Props = $ReadOnly<{||}>;
       type State = {|
         active: boolean,
@@ -316,7 +316,7 @@ exports.examples = [
   },
   {
     title: 'ZIndex',
-    render() {
+    render(): React.Node {
       type Props = $ReadOnly<{||}>;
       type State = {|
         flipped: boolean,
@@ -402,7 +402,7 @@ exports.examples = [
   },
   {
     title: 'BackfaceVisibility',
-    render: function() {
+    render: function(): React.Node {
       return (
         <>
           <Text style={{paddingBottom: 10}}>
diff --git a/RNTester/js/examples/XHR/XHRExample.js b/RNTester/js/examples/XHR/XHRExample.js
index b9e3ad37087bbe..c8871a01276f22 100644
--- a/RNTester/js/examples/XHR/XHRExample.js
+++ b/RNTester/js/examples/XHR/XHRExample.js
@@ -11,53 +11,51 @@
 'use strict';
 
 const React = require('react');
-
-const XHRExampleDownload = require('./XHRExampleDownload');
+const XHRExampleAbortController = require('./XHRExampleAbortController');
 const XHRExampleBinaryUpload = require('./XHRExampleBinaryUpload');
-const XHRExampleHeaders = require('./XHRExampleHeaders');
+const XHRExampleDownload = require('./XHRExampleDownload');
 const XHRExampleFetch = require('./XHRExampleFetch');
+const XHRExampleHeaders = require('./XHRExampleHeaders');
 const XHRExampleOnTimeOut = require('./XHRExampleOnTimeOut');
-const XHRExampleAbortController = require('./XHRExampleAbortController');
 
 exports.framework = 'React';
 exports.title = 'XMLHttpRequest';
-exports.description =
-  'Example that demonstrates upload and download ' +
-  'requests using XMLHttpRequest.';
+exports.description = ('Example that demonstrates upload and download ' +
+  'requests using XMLHttpRequest.': string);
 exports.examples = [
   {
     title: 'File Download',
-    render() {
+    render(): React.Node {
       return <XHRExampleDownload />;
     },
   },
   {
     title: 'multipart/form-data Upload',
-    render() {
+    render(): React.Node {
       return <XHRExampleBinaryUpload />;
     },
   },
   {
     title: 'Fetch Test',
-    render() {
+    render(): React.Node {
       return <XHRExampleFetch />;
     },
   },
   {
     title: 'Headers',
-    render() {
+    render(): React.Node {
       return <XHRExampleHeaders />;
     },
   },
   {
     title: 'Time Out Test',
-    render() {
+    render(): React.Node {
       return <XHRExampleOnTimeOut />;
     },
   },
   {
     title: 'Abort Test',
-    render() {
+    render(): React.Node {
       return <XHRExampleAbortController />;
     },
   },
diff --git a/RNTester/js/examples/XHR/XHRExampleAbortController.js b/RNTester/js/examples/XHR/XHRExampleAbortController.js
index 2d7b41d23061f4..f869098cc3e38b 100644
--- a/RNTester/js/examples/XHR/XHRExampleAbortController.js
+++ b/RNTester/js/examples/XHR/XHRExampleAbortController.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {Alert, Button, View} = require('react-native');
 
 class XHRExampleAbortController extends React.Component<{}, {}> {
@@ -35,7 +36,7 @@ class XHRExampleAbortController extends React.Component<{}, {}> {
     clearTimeout(this._timeout);
   }
 
-  render() {
+  render(): React.Node {
     return (
       <View>
         <Button
diff --git a/RNTester/js/examples/XHR/XHRExampleBinaryUpload.js b/RNTester/js/examples/XHR/XHRExampleBinaryUpload.js
index 59efcc192db182..962265116b187a 100644
--- a/RNTester/js/examples/XHR/XHRExampleBinaryUpload.js
+++ b/RNTester/js/examples/XHR/XHRExampleBinaryUpload.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {
   Alert,
   Linking,
@@ -71,7 +72,9 @@ class XHRExampleBinaryUpload extends React.Component<{}, $FlowFixMeState> {
     Linking.openURL(url);
   }
 
-  state = {
+  state:
+    | $FlowFixMe
+    | $TEMPORARY$object<{|type: $TEMPORARY$string<'Uint8Array'>|}> = {
     type: 'Uint8Array',
   };
 
@@ -104,7 +107,7 @@ class XHRExampleBinaryUpload extends React.Component<{}, $FlowFixMeState> {
     xhr.send(new TypedArrayClass(arrayBuffer));
   };
 
-  render() {
+  render(): React.Node {
     return (
       <View>
         <Text>Upload 255 bytes as...</Text>
diff --git a/RNTester/js/examples/XHR/XHRExampleDownload.js b/RNTester/js/examples/XHR/XHRExampleDownload.js
index 530e552b737d6c..15bb9e3e30b2b1 100644
--- a/RNTester/js/examples/XHR/XHRExampleDownload.js
+++ b/RNTester/js/examples/XHR/XHRExampleDownload.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {
   Alert,
   Platform,
@@ -142,7 +143,7 @@ class XHRExampleDownload extends React.Component<{}, Object> {
     this.xhr && this.xhr.abort();
   }
 
-  render() {
+  render(): React.Node {
     const button = this.state.downloading ? (
       <View style={styles.wrapper}>
         <View style={styles.button}>
diff --git a/RNTester/js/examples/XHR/XHRExampleFetch.js b/RNTester/js/examples/XHR/XHRExampleFetch.js
index d81275c775e52e..c9f4aa6bcafb8c 100644
--- a/RNTester/js/examples/XHR/XHRExampleFetch.js
+++ b/RNTester/js/examples/XHR/XHRExampleFetch.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {StyleSheet, Text, TextInput, View, Platform} = require('react-native');
 
 class XHRExampleFetch extends React.Component<any, any> {
@@ -57,7 +58,7 @@ class XHRExampleFetch extends React.Component<any, any> {
     return responseHeaders;
   }
 
-  render() {
+  render(): React.Node {
     const responseURL = this.responseURL ? (
       <View style={{marginTop: 10}}>
         <Text style={styles.label}>Server response URL:</Text>
diff --git a/RNTester/js/examples/XHR/XHRExampleOnTimeOut.js b/RNTester/js/examples/XHR/XHRExampleOnTimeOut.js
index dc25d4ef113c3a..e38f792ccd7f80 100644
--- a/RNTester/js/examples/XHR/XHRExampleOnTimeOut.js
+++ b/RNTester/js/examples/XHR/XHRExampleOnTimeOut.js
@@ -11,6 +11,7 @@
 'use strict';
 
 const React = require('react');
+
 const {StyleSheet, Text, TouchableHighlight, View} = require('react-native');
 
 class XHRExampleOnTimeOut extends React.Component<any, any> {
@@ -58,7 +59,7 @@ class XHRExampleOnTimeOut extends React.Component<any, any> {
     this.xhr && this.xhr.abort();
   }
 
-  render() {
+  render(): React.Node {
     const button = this.state.loading ? (
       <View style={styles.wrapper}>
         <View style={styles.button}>
diff --git a/RNTester/js/utils/RNTesterList.ios.js b/RNTester/js/utils/RNTesterList.ios.js
index f67f2bd2b2518e..4a9c7aa9442d54 100644
--- a/RNTester/js/utils/RNTesterList.ios.js
+++ b/RNTester/js/utils/RNTesterList.ios.js
@@ -337,7 +337,7 @@ const APIExamples: Array<RNTesterExample> = [
   },
 ];
 
-const Modules = {};
+const Modules: $TEMPORARY$object<{||}> = {};
 
 APIExamples.concat(ComponentExamples).forEach(Example => {
   Modules[Example.key] = Example.module;
diff --git a/ReactAndroid/src/androidTest/js/NativeIdTestModule.js b/ReactAndroid/src/androidTest/js/NativeIdTestModule.js
index 42093b323c95b0..cf4a67fe040fad 100644
--- a/ReactAndroid/src/androidTest/js/NativeIdTestModule.js
+++ b/ReactAndroid/src/androidTest/js/NativeIdTestModule.js
@@ -11,6 +11,8 @@
 'use strict';
 
 const React = require('react');
+const TouchableBounce = require('react-native/Libraries/Components/Touchable/TouchableBounce');
+
 const {
   Image,
   StyleSheet,
@@ -21,7 +23,6 @@ const {
   TouchableWithoutFeedback,
   View,
 } = require('react-native');
-const TouchableBounce = require('react-native/Libraries/Components/Touchable/TouchableBounce');
 
 /**
  * All the views implemented on Android, each with the nativeID property set.
@@ -30,7 +31,7 @@ const TouchableBounce = require('react-native/Libraries/Components/Touchable/Tou
  * - The nativeID property is passed to the native views
  */
 class NativeIdTestApp extends React.Component<{}> {
-  render() {
+  render(): React.Node {
     const uri =
       'data:image/gif;base64,' +
       'R0lGODdhMAAwAPAAAAAAAP///ywAAAAAMAAwAAAC8IyPqcvt3wCcDkiLc7C0qwyGHhSWpjQu5yqmCYsapy' +
diff --git a/ReactAndroid/src/androidTest/js/ScrollViewTestModule.js b/ReactAndroid/src/androidTest/js/ScrollViewTestModule.js
index 3e097245800083..d98f64ef73dab3 100644
--- a/ReactAndroid/src/androidTest/js/ScrollViewTestModule.js
+++ b/ReactAndroid/src/androidTest/js/ScrollViewTestModule.js
@@ -10,7 +10,9 @@
 
 'use strict';
 
+const BatchedBridge = require('react-native/Libraries/BatchedBridge/BatchedBridge');
 const React = require('react');
+
 const {
   NativeModules,
   ScrollView,
@@ -19,7 +21,6 @@ const {
   TouchableWithoutFeedback,
   View,
 } = require('react-native');
-const BatchedBridge = require('react-native/Libraries/BatchedBridge/BatchedBridge');
 
 const {ScrollListener} = NativeModules;
 
@@ -94,8 +95,8 @@ class ScrollViewTestApp extends React.Component<Props, State> {
   /* $FlowFixMe(>=0.87.0 site=react_native_fb) This comment suppresses an error
    * found when Flow v0.87 was deployed. To see the error, delete this comment
    * and run Flow. */
-  scrollView = React.createRef();
-  state = getInitialState();
+  scrollView: {|current: any | null|} = React.createRef();
+  state: State = getInitialState();
 
   scrollTo(destX: number, destY: number) {
     const scrollView = this.scrollView.current;
@@ -106,7 +107,7 @@ class ScrollViewTestApp extends React.Component<Props, State> {
     scrollView.scrollTo(destY, destX);
   }
 
-  render() {
+  render(): React.Node {
     scrollViewApp = this;
     const children = this.state.data.map((item, index) => (
       <Item
@@ -131,8 +132,8 @@ class HorizontalScrollViewTestApp extends React.Component<Props, State> {
   /* $FlowFixMe(>=0.87.0 site=react_native_fb) This comment suppresses an error
    * found when Flow v0.87 was deployed. To see the error, delete this comment
    * and run Flow. */
-  scrollView = React.createRef();
-  state = getInitialState();
+  scrollView: {|current: any | null|} = React.createRef();
+  state: State = getInitialState();
 
   scrollTo(destX: number, destY: number) {
     const scrollView = this.scrollView.current;
@@ -143,7 +144,7 @@ class HorizontalScrollViewTestApp extends React.Component<Props, State> {
     scrollView.scrollTo(destY, destX);
   }
 
-  render() {
+  render(): React.Node {
     scrollViewApp = this;
     const children = this.state.data.map((item, index) => (
       <Item
diff --git a/ReactAndroid/src/androidTest/js/UIManagerTestModule.js b/ReactAndroid/src/androidTest/js/UIManagerTestModule.js
index 781d0aceba006e..06b85decd3931b 100644
--- a/ReactAndroid/src/androidTest/js/UIManagerTestModule.js
+++ b/ReactAndroid/src/androidTest/js/UIManagerTestModule.js
@@ -10,11 +10,13 @@
 
 'use strict';
 
-const React = require('react');
-const {StyleSheet, Text, View} = require('react-native');
 const BatchedBridge = require('react-native/Libraries/BatchedBridge/BatchedBridge');
+const React = require('react');
+
 const renderApplication = require('react-native/Libraries/ReactNative/renderApplication');
 
+const {StyleSheet, Text, View} = require('react-native');
+
 type FlexTestAppProps = $ReadOnly<{||}>;
 class FlexTestApp extends React.Component<FlexTestAppProps> {
   render() {
@@ -171,7 +173,7 @@ const CenteredTextViewStyles = StyleSheet.create({
   },
 });
 
-let flushUpdatePositionInList = null;
+let flushUpdatePositionInList: null | (() => void) = null;
 
 type UpdatePositionInListTestAppProps = $ReadOnly<{||}>;
 type UpdatePositionInListTestAppState = {|
diff --git a/ReactCommon/hermes/inspector/tools/msggen/src/Converters.js b/ReactCommon/hermes/inspector/tools/msggen/src/Converters.js
index f8dd5f8c047103..66e403f5782e6d 100644
--- a/ReactCommon/hermes/inspector/tools/msggen/src/Converters.js
+++ b/ReactCommon/hermes/inspector/tools/msggen/src/Converters.js
@@ -9,11 +9,11 @@
  */
 'use strict';
 
-export function toCppNamespace(domain: string) {
+export function toCppNamespace(domain: string): string {
   return domain.substr(0, 1).toLowerCase() + domain.substr(1);
 }
 
-export function toCppType(type: string) {
+export function toCppType(type: string): string {
   return type.substr(0, 1).toUpperCase() + type.substr(1);
 }
 
diff --git a/ReactCommon/hermes/inspector/tools/msggen/src/GeneratedHeader.js b/ReactCommon/hermes/inspector/tools/msggen/src/GeneratedHeader.js
index 775d459ee6576f..5db13fa0a40d16 100644
--- a/ReactCommon/hermes/inspector/tools/msggen/src/GeneratedHeader.js
+++ b/ReactCommon/hermes/inspector/tools/msggen/src/GeneratedHeader.js
@@ -10,6 +10,6 @@
 'use strict';
 
 // placeholder token that will be replaced by signedsource script
-export const GeneratedHeader =
+export const GeneratedHeader: string =
   '// Copyright 2004-present Facebook. All Rights Reserved.\n' +
   '// @generated <<SignedSource::*O*zOeWoEQle#+L!plEphiEmie@IsG>>';
diff --git a/jest/preprocessor.js b/jest/preprocessor.js
index 79af17267667e7..5920c0a6f23c05 100644
--- a/jest/preprocessor.js
+++ b/jest/preprocessor.js
@@ -12,9 +12,10 @@
 
 'use strict';
 
-const {transformSync: babelTransformSync} = require('@babel/core');
 const babelRegisterOnly = require('metro-babel-register');
 const createCacheKeyFunction = require('fbjs-scripts/jest/createCacheKeyFunction');
+
+const {transformSync: babelTransformSync} = require('@babel/core');
 const generate = require('@babel/generator').default;
 
 const nodeFiles = new RegExp(
@@ -28,7 +29,7 @@ babelRegisterOnly([]);
 
 const transformer = require('metro-react-native-babel-transformer');
 module.exports = {
-  process(src /*: string */, file /*: string */) {
+  process(src /*: string */, file /*: string */) /*: string */ {
     if (nodeFiles.test(file)) {
       // node specific transforms only
       return babelTransformSync(src, {
@@ -111,9 +112,9 @@ module.exports = {
     ).code;
   },
 
-  getCacheKey: createCacheKeyFunction([
+  getCacheKey: (createCacheKeyFunction([
     __filename,
     require.resolve('metro-react-native-babel-transformer'),
     require.resolve('@babel/core/package.json'),
-  ]),
+  ]) /*: any */),
 };
diff --git a/jest/renderer.js b/jest/renderer.js
index 26c6e8b3acd5f8..66777228da64a4 100644
--- a/jest/renderer.js
+++ b/jest/renderer.js
@@ -12,18 +12,17 @@
 'use strict';
 
 const React = require('react');
-
-const TestRenderer = require('react-test-renderer');
 const ShallowRenderer = require('react-test-renderer/shallow');
+const TestRenderer = require('react-test-renderer');
 
 const renderer = new ShallowRenderer();
 
-export const shallow = (Component: React.Element<any>) => {
+export const shallow = (Component: React.Element<any>): any => {
   const Wrapper = (): React.Element<any> => Component;
 
   return renderer.render(<Wrapper />);
 };
 
-export const create = (Component: React.Element<any>) => {
+export const create = (Component: React.Element<any>): any => {
   return TestRenderer.create(Component);
 };
diff --git a/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeArrayTurboModule.js b/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeArrayTurboModule.js
index f421bafb68477f..cd21a54d719397 100644
--- a/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeArrayTurboModule.js
+++ b/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeArrayTurboModule.js
@@ -22,4 +22,6 @@ export interface Spec extends TurboModule {
   +getArrayWithAlias: (a: AnotherArray, b: Array<ArrayType>) => AnotherArray;
 }
 
-export default TurboModuleRegistry.getEnforcing<Spec>('SampleTurboModule');
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'SampleTurboModule',
+): Spec);
diff --git a/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeBooleanTurboModule.js b/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeBooleanTurboModule.js
index 7b332af37a3fab..f698ed71c569bd 100644
--- a/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeBooleanTurboModule.js
+++ b/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeBooleanTurboModule.js
@@ -21,4 +21,6 @@ export interface Spec extends TurboModule {
   +getBooleanWithAlias: (arg: Boolean) => AnotherBoolean;
 }
 
-export default TurboModuleRegistry.getEnforcing<Spec>('SampleTurboModule');
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'SampleTurboModule',
+): Spec);
diff --git a/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeCallbackTurboModule.js b/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeCallbackTurboModule.js
index 3ad70c62f44ad0..c23cfa77a1bc0c 100644
--- a/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeCallbackTurboModule.js
+++ b/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeCallbackTurboModule.js
@@ -21,4 +21,6 @@ export interface Spec extends TurboModule {
   +getValueWithCallbackWithAlias: (c: CB) => void;
 }
 
-export default TurboModuleRegistry.getEnforcing<Spec>('SampleTurboModule');
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'SampleTurboModule',
+): Spec);
diff --git a/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeNumberTurboModule.js b/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeNumberTurboModule.js
index 8b63fda94511ee..41ce0787712df1 100644
--- a/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeNumberTurboModule.js
+++ b/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeNumberTurboModule.js
@@ -21,4 +21,6 @@ export interface Spec extends TurboModule {
   +getNumberWithAlias: (arg: Number) => AnotherNumber;
 }
 
-export default TurboModuleRegistry.getEnforcing<Spec>('SampleTurboModule');
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'SampleTurboModule',
+): Spec);
diff --git a/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeObjectTurboModule.js b/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeObjectTurboModule.js
index 2f9b3b936a6f73..6400942e175f2a 100644
--- a/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeObjectTurboModule.js
+++ b/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeObjectTurboModule.js
@@ -60,4 +60,6 @@ export interface Spec extends TurboModule {
   |};
 }
 
-export default TurboModuleRegistry.getEnforcing<Spec>('SampleTurboModule');
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'SampleTurboModule',
+): Spec);
diff --git a/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeOptionalObjectTurboModule.js b/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeOptionalObjectTurboModule.js
index e53d24df29f6b0..b697ab954dd573 100644
--- a/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeOptionalObjectTurboModule.js
+++ b/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeOptionalObjectTurboModule.js
@@ -35,4 +35,6 @@ export interface Spec extends TurboModule {
   |};
 }
 
-export default TurboModuleRegistry.getEnforcing<Spec>('SampleTurboModule');
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'SampleTurboModule',
+): Spec);
diff --git a/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativePromiseTurboModule.js b/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativePromiseTurboModule.js
index 79dbf9add85c9b..2ccd30546a2413 100644
--- a/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativePromiseTurboModule.js
+++ b/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativePromiseTurboModule.js
@@ -21,4 +21,6 @@ export interface Spec extends TurboModule {
   +getValueWithPromiseWithAlias: (arg: String) => AnotherPromise;
 }
 
-export default TurboModuleRegistry.getEnforcing<Spec>('SampleTurboModule');
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'SampleTurboModule',
+): Spec);
diff --git a/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeSampleTurboModule.js b/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeSampleTurboModule.js
index 9088caea859eac..ee6c0983afb75f 100644
--- a/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeSampleTurboModule.js
+++ b/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeSampleTurboModule.js
@@ -31,4 +31,6 @@ export interface Spec extends TurboModule {
   +getValueWithPromise: (error: boolean) => Promise<string>;
 }
 
-export default TurboModuleRegistry.getEnforcing<Spec>('SampleTurboModule');
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'SampleTurboModule',
+): Spec);
diff --git a/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeStringTurboModule.js b/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeStringTurboModule.js
index 2369153a43064a..4c844d39056c12 100644
--- a/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeStringTurboModule.js
+++ b/packages/react-native-codegen/e2e/__test_fixtures__/modules/NativeStringTurboModule.js
@@ -21,4 +21,6 @@ export interface Spec extends TurboModule {
   +getStringWithAlias: (arg: String) => AnotherString;
 }
 
-export default TurboModuleRegistry.getEnforcing<Spec>('SampleTurboModule');
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'SampleTurboModule',
+): Spec);
diff --git a/packages/react-native-codegen/src/generators/components/EventEmitterHelpers.js b/packages/react-native-codegen/src/generators/components/EventEmitterHelpers.js
index b4f3a41a53677a..665d504fe179ff 100644
--- a/packages/react-native-codegen/src/generators/components/EventEmitterHelpers.js
+++ b/packages/react-native-codegen/src/generators/components/EventEmitterHelpers.js
@@ -17,7 +17,7 @@ const {toSafeCppString} = require('./CppHelpers.js');
 function generateStructName(
   componentName: string,
   parts: $ReadOnlyArray<string> = [],
-) {
+): string {
   const additional = parts.map(toSafeCppString).join('');
   return `${componentName}${additional}Struct`;
 }