Issue 4795 - Use modern JavaScript syntax

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");
+const {EventEmitter} = require("events");
 
 /**
  * Communication port wrapping ext.onMessage to receive messages.
  *
  * @constructor
  */
 function Port()
 {
   this._eventEmitter = new EventEmitter();
   this._onMessage = this._onMessage.bind(this);
   ext.onMessage.addListener(this._onMessage);
 };
 
 Port.prototype = {
-  _onMessage: function(message, sender, sendResponse)
+  _onMessage(message, sender, sendResponse)
   {
     let async = false;
     let callbacks = this._eventEmitter.listeners(message.type);
 
     for (let callback of callbacks)
     {
       let response = callback(message, sender);
 
       if (response && typeof response.then == "function")
       {
@@ skipping 26 matching lines @@
    *         or a promise (asynchronous response).
    */
 
   /**
    * 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)
+  on(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)
+  off(name, callback)
   {
     this._eventEmitter.off(name, callback);
   },
 
   /**
    * Disables the port and makes it stop listening to incoming messages.
    */
-  disconnect: function()
+  disconnect()
   {
     ext.onMessage.removeListener(this._onMessage);
   }
 };
 
 /**
  * The default port to receive messages.
  *
  * @type {Port}
  */
 exports.port = new Port();
 
 /**
  * Creates a new port that is disconnected when the given window is unloaded.
  *
  * @param {Window} window
  * @return {Port}
  */
 exports.getPort = function(window)
 {
   let port = new Port();
   window.addEventListener("unload", () =>
   {
     port.disconnect();
   });
   return port;
 };