Issue 3826 - Filter preference change events

lib/messaging.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2016 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/>.
  */
 
 /** @module messaging */
 
 "use strict";
 
+let {EventEmitter} = require("events");
+
 /**
  * Communication port wrapping ext.onMessage to receive messages.
  *
  * @constructor
  */
 function Port()
 {
-  this._callbacks = Object.create(null);
+  this._eventEmitter = new EventEmitter();
   ext.onMessage.addListener(this._onMessage.bind(this));
 };
 
 Port.prototype = {
   _onMessage: function(message, sender, sendResponse)
   {
     let async = false;
-    let callbacks = this._callbacks[message.type] || [];
+    let callbacks = this._eventEmitter._callbacks[message.type] || [];
 
     for (let callback of callbacks)
     {
       let response = callback(message, sender);
 
       if (response instanceof Promise)
       {
         response.then(
           sendResponse,
           reason => {
@@ skipping 25 matching lines @@
 
   /**
    * Adds a callback for the specified message.
    *
    * The return value of the callback (if not undefined) is sent as response.
    * @param {string}   name
    * @param {Port~messageCallback} callback
    */
   on: function(name, callback)
   {
-    if (name in this._callbacks)
-      this._callbacks[name].push(callback);
-    else
-      this._callbacks[name] = [callback];
+    this._eventEmitter.on(name, callback);
   },
 
   /**
    * Removes a callback for the specified message.
    *
    * @param {string}   name
    * @param {Port~messageCallback} callback
    */
   off: function(name, callback)
   {
-    let callbacks = this._callbacks[name];
-    if (callbacks)
-    {
-      let idx = callbacks.indexOf(callback);
-      if (idx != -1)
-        callbacks.splice(idx, 1);
-    }
+    this._eventEmitter.off(name, callback);
   }
 };
 
 /**
  * The default port to receive messages.
  *
  * @type {Port}
  */
 exports.port = new Port();