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react-ui/events

This package is experimental. It is intended for use with the experimental React events API that is not available in open source builds.

Event Responders attach to a host node. They listen to native browser events dispatched on the host node of their child and transform those events into high-level events for applications.

The core API is documented below. Documentation for individual Event Responders can be found here.

Event Responder Interface

An Event Responder Interface is defined using an object. Each responder can define DOM events to listen to, handle the synthetic responder events, dispatch custom events, and implement a state machine.

// types
type ResponderEventType = string;

type ResponderEvent = {|
  nativeEvent: any,
  target: Element | Document,
  pointerType: string,
  type: string,
  passive: boolean,
  passiveSupported: boolean,
|};

type CustomEvent = {
  type: string,
  target: Element,
  ...
}

getInitialState?: (props: null | Object) => Object

The initial state of that the Event Responder is created with.

onEvent?: (event: ResponderEvent, context: ResponderContext, props, state)

Called during the bubble phase of the targetEventTypes dispatched on DOM elements within the Event Responder.

onMount?: (context: ResponderContext, props, state)

Called after an Event Responder in mounted.

onRootEvent?: (event: ResponderEvent, context: ResponderContext, props, state)

Called when any of the rootEventTypes are dispatched on the root of the app.

onUnmount?: (context: ResponderContext, props, state)

Called before an Event Responder in unmounted.

rootEventTypes?: Array

Defines the DOM events to listen to on the root of the app.

targetEventTypes?: Array

Defines the DOM events to listen to within the Event Responder subtree.

ResponderContext

The Event Responder Context is exposed via the context argument for certain methods on the EventResponder object.

addRootEventTypes(eventTypes: Array)

This can be used to dynamically listen to events on the root of the app only when it is necessary to do so.

clearTimeout(id: Symbol): void

Clear a timeout defined using context.setTimeout.

dispatchEvent(propName: string, event: CustomEvent, { discrete: boolean })

Dispatches a custom synthetic event. The type and target are required fields if the event is an object, but any other fields can be defined on the event that will be passed to the listener. You can also pass a value that is not an object, but a boolean. For example:

const event = { type: 'press', target, pointerType, x, y };
context.dispatchEvent('onPress', event, DiscreteEvent);

isTargetWithinNode(target: Element, element: Element): boolean

Returns true if target is a child of element.

isTargetWithinResponder(target: Element): boolean

Returns true is the target element is within the subtree of the Event Responder.

isTargetWithinResponderScope(target: Element): boolean

Returns true is the target element is within the current Event Responder's scope. If the target element is within the scope of the same responder, but owned by another Event Responder instance, this will return false.

removeRootEventTypes(eventTypes: Array)

Remove the root event types added with addRootEventTypes.

setTimeout(func: () => void, delay: number): Symbol

This can be used to dispatch async events, e.g., those that fire after a delay.