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fix: faster shallowEqual 30% performance improvement & __DEV__ Just make a judgment once #28776

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fix: faster shallowEqual 30% performance improvement & __DEV__ Just make a judgment once #28776

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c983d1c
fix: `__DEV__` Just make a judgment once
jeryqwq Apr 7, 2024
a114460
perf: faster shallowEqual more 30% https://jsben.ch/MQb2y
jeryqwq Apr 7, 2024
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12 changes: 5 additions & 7 deletions packages/react/src/ReactMemo.js
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Expand Up @@ -15,6 +15,11 @@ export function memo<Props>(
type: React$ElementType,
compare?: (oldProps: Props, newProps: Props) => boolean,
) {
const elementType = {
$$typeof: REACT_MEMO_TYPE,
type,
compare: compare === undefined ? null : compare,
};
if (__DEV__) {
if (!isValidElementType(type)) {
console.error(
Expand All @@ -23,13 +28,6 @@ export function memo<Props>(
type === null ? 'null' : typeof type,
);
}
}
const elementType = {
$$typeof: REACT_MEMO_TYPE,
type,
compare: compare === undefined ? null : compare,
};
if (__DEV__) {
let ownName;
Object.defineProperty(elementType, 'displayName', {
enumerable: false,
Expand Down
25 changes: 10 additions & 15 deletions packages/shared/shallowEqual.js
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Expand Up @@ -29,26 +29,21 @@ function shallowEqual(objA: mixed, objB: mixed): boolean {
return false;
}

const keysA = Object.keys(objA);
const keysB = Object.keys(objB);
let aLength = 0;
let bLength = 0;

if (keysA.length !== keysB.length) {
return false;
}

// Test for A's keys different from B.
for (let i = 0; i < keysA.length; i++) {
const currentKey = keysA[i];
if (
!hasOwnProperty.call(objB, currentKey) ||
// $FlowFixMe[incompatible-use] lost refinement of `objB`
!is(objA[currentKey], objB[currentKey])
) {
for (const key in objA) {
aLength += 1;
if (!hasOwnProperty.call(objB, key) || !is(objA[key], objB[key])) {
return false;
}
}

return true;
for (const _ in objB) {
bLength += 1;
}

return aLength === bLength;
}

export default shallowEqual;