Issue 4795 - Use modern JavaScript syntax

ext/background.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/>.
  */
 
-(function()
+"use strict";
+
 {
-  var nonEmptyPageMaps = Object.create(null);
-  var pageMapCounter = 0;
+  let nonEmptyPageMaps = Object.create(null);

[Sebastian Noack, 2017/01/16 14:47:40]

In "modern JavaScript" you wouldn't (mis)use objects as hashtable, but use Map
objects instead. Not sure whether it is worth to change this, if it is only for
the to be removed abstraction layer. But there might be more occurrences of this
pattern.

[kzar, 2017/01/16 14:59:07]

Good point, but would you mind if we left that for a second review? This is
already getting fairly unwieldly.

[Sebastian Noack, 2017/01/16 15:35:54]

Acknowledged.

+  let pageMapCounter = 0;
 
-  var PageMap = ext.PageMap = function()
+  let PageMap = ext.PageMap = function()
   {
     this._map = Object.create(null);
     this._id = ++pageMapCounter;
   };
   PageMap.prototype = {
-    _delete: function(id)
+    _delete(id)
     {
       delete this._map[id];
 
       if (Object.keys(this._map).length == 0)
         delete nonEmptyPageMaps[this._id];
     },
-    keys: function()
+    keys()
     {
       return Object.keys(this._map).map(ext.getPage);
     },
-    get: function(page)
+    get(page)
     {
       return this._map[page.id];
     },
-    set: function(page, value)
+    set(page, value)
     {
       this._map[page.id] = value;
       nonEmptyPageMaps[this._id] = this;
     },
-    has: function(page)
+    has(page)
     {
       return page.id in this._map;
     },
-    clear: function()
+    clear()
     {
-      for (var id in this._map)
+      for (let id in this._map)
         this._delete(id);
     },
-    delete: function(page)
+    delete(page)
     {
       this._delete(page.id);
     }
   };
 
-  ext._removeFromAllPageMaps = function(pageId)
+  ext._removeFromAllPageMaps = pageId =>
   {
-    for (var pageMapId in nonEmptyPageMaps)
+    for (let pageMapId in nonEmptyPageMaps)
       nonEmptyPageMaps[pageMapId]._delete(pageId);
   };
-})();
+}