src/EventEmitter.ts

   1 /**
   2  * @license MIT
   3  */
   4
   5 import { IEventEmitter } from './Interfaces';
   6
   7 interface ListenerType {
   8     (): void;
   9     listener?: () => void;
  10 };
  11
  12 export class EventEmitter implements IEventEmitter {
  13   private _events: {[type: string]: ListenerType[]};
  14
  15   constructor() {
  16     // Restore the previous events if available, this will happen if the
  17     // constructor is called multiple times on the same object (terminal reset).
  18     this._events = this._events || {};
  19   }
  20
  21   public on(type, listener): void {
  22     this._events[type] = this._events[type] || [];
  23     this._events[type].push(listener);
  24   }
  25
  26   public off(type, listener): void {
  27     if (!this._events[type]) {
  28       return;
  29     }
  30
  31     let obj = this._events[type];
  32     let i = obj.length;
  33
  34     while (i--) {
  35       if (obj[i] === listener || obj[i].listener === listener) {
  36         obj.splice(i, 1);
  37         return;
  38       }
  39     }
  40   }
  41
  42   public removeAllListeners(type): void {
  43     if (this._events[type]) {
  44        delete this._events[type];
  45     }
  46   }
  47
  48   public once(type, listener): any {
  49     function on() {
  50       let args = Array.prototype.slice.call(arguments);
  51       this.off(type, on);
  52       return listener.apply(this, args);
  53     }
  54     (<any>on).listener = listener;
  55     return this.on(type, on);
  56   }
  57
  58   public emit(type: string, ...args: any[]): void {
  59     if (!this._events[type]) {
  60       return;
  61     }
  62     let obj = this._events[type];
  63     for (let i = 0; i < obj.length; i++) {
  64       obj[i].apply(this, args);
  65     }
  66   }
  67
  68   public listeners(type): ListenerType[] {
  69     return this._events[type] || [];
  70   }
  71 }