Function patchEvents

packages/zone.js/lib/node/events.ts:12–67

(Zone: ZoneType)

import {ZoneType} from '../zone-impl';

export function patchEvents(Zone: ZoneType): void {
  Zone.__load_patch('EventEmitter', (global: any, Zone: ZoneType, api: _ZonePrivate) => {
    // For EventEmitter
    const EE_ADD_LISTENER = 'addListener';
    const EE_PREPEND_LISTENER = 'prependListener';
    const EE_REMOVE_LISTENER = 'removeListener';
    const EE_REMOVE_ALL_LISTENER = 'removeAllListeners';
    const EE_LISTENERS = 'listeners';
    const EE_ON = 'on';
    const EE_OFF = 'off';

    const compareTaskCallbackVsDelegate = function (task: any, delegate: any) {
      // same callback, same capture, same event name, just return
      return task.callback === delegate || task.callback.listener === delegate;
    };

    const eventNameToString = function (eventName: string | Symbol) {
      if (typeof eventName === 'string') {
        return eventName;
      }
      if (!eventName) {
        return '';
      }
      return eventName.toString().replace('(', '_').replace(')', '_');
    };

    function patchEventEmitterMethods(obj: any) {
      const result = patchEventTarget(global, api, [obj], {
        useG: false,
        add: EE_ADD_LISTENER,
        rm: EE_REMOVE_LISTENER,
        prepend: EE_PREPEND_LISTENER,
        rmAll: EE_REMOVE_ALL_LISTENER,
        listeners: EE_LISTENERS,
        chkDup: false,
        rt: true,
        diff: compareTaskCallbackVsDelegate,
        eventNameToString: eventNameToString,
      });
      if (result && result[0]) {
        obj[EE_ON] = obj[EE_ADD_LISTENER];
        obj[EE_OFF] = obj[EE_REMOVE_LISTENER];
      }
    }

    // EventEmitter
    let events;
    try {
      events = require('events');
    } catch (err) {}

    if (events && events.EventEmitter) {
      patchEventEmitterMethods(events.EventEmitter.prototype);
    }
  });
}