core/util/eventtarget.js

   1 /*
   2  * noVNC: HTML5 VNC client
   3  * Copyright 2017 Pierre Ossman for Cendio AB
   4  * Licensed under MPL 2.0 (see LICENSE.txt)
   5  *
   6  * See README.md for usage and integration instructions.
   7  */
   8
   9 const EventTargetMixin = {
  10     _listeners: null,
  11
  12    addEventListener: function(type, callback) {
  13       if (!this._listeners) {
  14          this._listeners = new Map();
  15       }
  16       if (!this._listeners.has(type)) {
  17          this._listeners.set(type, new Set());
  18       }
  19       this._listeners.get(type).add(callback);
  20    },
  21
  22    removeEventListener: function(type, callback) {
  23       if (!this._listeners || !this._listeners.has(type)) {
  24          return;
  25       }
  26       this._listeners.get(type).delete(callback);
  27    },
  28
  29    dispatchEvent: function(event) {
  30       if (!this._listeners || !this._listeners.has(event.type)) {
  31          return true;
  32       }
  33       this._listeners.get(event.type).forEach(function (callback) {
  34          callback.call(this, event);
  35       }, this);
  36       return !event.defaultPrevented;
  37    },
  38 };
  39
  40 export default EventTargetMixin;