src/EventEmitter.ts

   1 /**
   2  * @license MIT
   3  */
   4
   5 interface ListenerType {
   6     (): void;
   7     listener?: () => void;
   8 };
   9
  10 export class EventEmitter {
  11   private _events: {[type: string]: ListenerType[]};
  12
  13   constructor() {
  14     this._events = {};
  15   }
  16
  17   public on(type, listener): void {
  18     this._events[type] = this._events[type] || [];
  19     this._events[type].push(listener);
  20   }
  21
  22   public off(type, listener): void {
  23     if (!this._events[type]) {
  24       return;
  25     }
  26
  27     let obj = this._events[type];
  28     let i = obj.length;
  29
  30     while (i--) {
  31       if (obj[i] === listener || obj[i].listener === listener) {
  32         obj.splice(i, 1);
  33         return;
  34       }
  35     }
  36   }
  37
  38   public removeAllListeners(type): void {
  39     if (this._events[type]) {
  40        delete this._events[type];
  41     }
  42   }
  43
  44   public once(type, listener): any {
  45     function on() {
  46       let args = Array.prototype.slice.call(arguments);
  47       this.off(type, on);
  48       return listener.apply(this, args);
  49     }
  50     (<any>on).listener = listener;
  51     return this.on(type, on);
  52   }
  53
  54   public emit(type): void {
  55     if (!this._events[type]) {
  56       return;
  57     }
  58
  59     let args = Array.prototype.slice.call(arguments, 1);
  60     let obj = this._events[type];
  61
  62     for (let i = 0; i < obj.length; i++) {
  63       obj[i].apply(this, args);
  64     }
  65   }
  66
  67   public listeners(type): ListenerType[] {
  68     return this._events[type] || [];
  69   }
  70 }