Noissue - Use Map to store EventEmitter listeners

lib/events.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 "use strict";
 
 /**
  * Registers and emits named events.
  *
  * @constructor
  */
 exports.EventEmitter = function()
 {
-  this._listeners = Object.create(null);
+  this._listeners = new Map();
 };
 
 exports.EventEmitter.prototype = {
   /**
    * Adds a listener for the specified event name.
    *
    * @param {string}   name
    * @param {function} listener
    */
   on(name, listener)
   {
-    if (name in this._listeners)
-      this._listeners[name].push(listener);
+    let listeners = this._listeners.get(name);
+    if (listeners)
+      listeners.push(listener);
     else
-      this._listeners[name] = [listener];
+      this._listeners.set(name, [listener]);
   },
 
   /**
    * Removes a listener for the specified event name.
    *
    * @param {string}   name
    * @param {function} listener
    */
   off(name, listener)
   {
-    let listeners = this._listeners[name];
+    let listeners = this._listeners.get(name);
     if (listeners)
     {
       let idx = listeners.indexOf(listener);
       if (idx != -1)
         listeners.splice(idx, 1);
     }
   },
 
   /**
    * Adds a one time listener and returns a promise that
@@ skipping 16 matching lines @@
   },
 
   /**
    * Returns a copy of the array of listeners for the specified event.
    *
    * @param {string} name
    * @return {function[]}
    */
   listeners(name)
   {
-    let listeners = this._listeners[name];
+    let listeners = this._listeners.get(name);
     return listeners ? listeners.slice() : [];
   },
 
   /**
    * Calls all previously added listeners for the given event name.
    *
    * @param {string} name
    * @param {...*}   [arg]
    */
   emit(name, ...args)
   {
     let listeners = this.listeners(name);
     for (let listener of listeners)
       listener(...args);
   }
 };