SyntheticEvent.js — react Source File

Source Code

/**
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @flow
 */

/* eslint valid-typeof: 0 */

import type {Fiber} from 'react-reconciler/src/ReactInternalTypes';

import assign from 'shared/assign';
import getEventCharCode from './getEventCharCode';

type EventInterfaceType = {
  [propName: string]: 0 | ((event: {[propName: string]: mixed, ...}) => mixed),
};

function functionThatReturnsTrue() {
  return true;
}

function functionThatReturnsFalse() {
  return false;
}

// This is intentionally a factory so that we have different returned constructors.
// If we had a single constructor, it would be megamorphic and engines would deopt.
function createSyntheticEvent(Interface: EventInterfaceType) {
  /**
   * Synthetic events are dispatched by event plugins, typically in response to a
   * top-level event delegation handler.
   *
   * These systems should generally use pooling to reduce the frequency of garbage
   * collection. The system should check `isPersistent` to determine whether the
   * event should be released into the pool after being dispatched. Users that
   * need a persisted event should invoke `persist`.
   *
   * Synthetic events (and subclasses) implement the DOM Level 3 Events API by
   * normalizing browser quirks. Subclasses do not necessarily have to implement a
   * DOM interface; custom application-specific events can also subclass this.
   */
  // $FlowFixMe[missing-this-annot]
  function SyntheticBaseEvent(
    reactName: string | null,
    reactEventType: string,
    targetInst: Fiber | null,
    nativeEvent: {[propName: string]: mixed, ...},
    nativeEventTarget: null | EventTarget,
  ) {
    this._reactName = reactName;
    this._targetInst = targetInst;
    this.type = reactEventType;
    this.nativeEvent = nativeEvent;
    this.target = nativeEventTarget;
    this.currentTarget = null;

    for (const propName in Interface) {
// ... (555 more lines)