Use fat arrow functions `const foo = () => { ... };` for callbacks

[mirror_novnc.git] / core / util / eventtarget.js

/*
 * noVNC: HTML5 VNC client
 * Copyright 2017 Pierre Ossman for Cendio AB
 * Licensed under MPL 2.0 (see LICENSE.txt)
 *
 * See README.md for usage and integration instructions.
 */

export default class EventTargetMixin {
    constructor() {
        this._listeners = null;
    }

   addEventListener(type, callback) {
      if (!this._listeners) {
         this._listeners = new Map();
      }
      if (!this._listeners.has(type)) {
         this._listeners.set(type, new Set());
      }
      this._listeners.get(type).add(callback);
   }

   removeEventListener(type, callback) {
      if (!this._listeners || !this._listeners.has(type)) {
         return;
      }
      this._listeners.get(type).delete(callback);
   }

   dispatchEvent(event) {
      if (!this._listeners || !this._listeners.has(event.type)) {
         return true;
      }
      this._listeners.get(event.type).forEach((callback) => {
         callback.call(this, event);
      }, this);
      return !event.defaultPrevented;
   }
}