Issue 4795 - Use modern JavaScript syntax

lib/io.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/>.
  */
 
 const keyPrefix = "file:";
 
 function fileToKey(file)
 {
   return keyPrefix + (file instanceof FakeFile ? file.path : file.spec);
 }
 
 function loadFile(file, successCallback, errorCallback)
 {
   let key = fileToKey(file);
 
-  ext.storage.get([key], function(items)
+  ext.storage.get([key], items =>
   {
     let entry = items[key];
 
     if (entry)
       successCallback(entry);
     else
       errorCallback(new Error("File doesn't exist"));
   });
 }
 
 function saveFile(file, data, callback)
 {
   ext.storage.set(
     fileToKey(file),
     {
       content: Array.from(data),
       lastModified: Date.now()
     },
     callback
   );
 }
 
 exports.IO =
 {
-  resolveFilePath: function(path)
-  {
-    return new FakeFile(path);
-  },
+  resolveFilePath: path => new FakeFile(path),
 
-  readFromFile: function(file, listener, callback)
+  readFromFile: (file, listener, callback) =>
   {
     function onLoaded(entry)
     {
       for (let line of entry.content)
         listener.process(line);
 
       listener.process(null);
       callback(null);
     }
 
     loadFile(file, onLoaded, callback);
   },
 
-  writeToFile: function(file, data, callback)
+  writeToFile: (file, data, callback) =>
   {
     saveFile(file, data, callback);
   },
 
-  copyFile: function(fromFile, toFile, callback)
+  copyFile: (fromFile, toFile, callback) =>
   {
     function onLoaded(entry)
     {
       saveFile(toFile, entry.content, callback);
     }
 
     loadFile(fromFile, onLoaded, callback);
   },
 
-  renameFile: function(fromFile, newName, callback)
+  renameFile: (fromFile, newName, callback) =>
   {
     function onLoaded(entry)
     {
-      ext.storage.remove(fileToKey(fromFile), function()
+      ext.storage.remove(fileToKey(fromFile), () =>
       {
         ext.storage.set(keyPrefix + newName, entry, callback);
       });
     }
 
     loadFile(fromFile, onLoaded, callback);
   },
 
-  removeFile: function(file, callback)
+  removeFile: (file, callback) =>
   {
     ext.storage.remove(fileToKey(file), callback);
   },
 
-  statFile: function(file, callback)
+  statFile: (file, callback) =>
   {
     function onLoaded(entry)
     {
       callback(null, {
         exists: true,
         lastModified: entry.lastModified
       });
     }
 
     loadFile(file, onLoaded, callback);
   }
 };