Issue 4795 - Use modern JavaScript syntax

lib/prefs.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
@@ skipping 170 matching lines @@
   * @static
   */
 let Prefs = exports.Prefs = {
   /**
    * Adds a callback that is called when the
    * value of a specified preference changed.
    *
    * @param {string}   preference
    * @param {function} callback
    */
-  on: function(preference, callback)
+  on: (preference, callback) =>
   {
     eventEmitter.on(preference, callback);
   },
 
   /**
    * Removes a callback for the specified preference.
    *
    * @param {string}   preference
    * @param {function} callback
    */
-  off: function(preference, callback)
+  off: (preference, callback) =>
   {
     eventEmitter.off(preference, callback);
   },
 
   /**
    * A promise that is fullfilled when all preferences have been loaded.
    * Wait for this promise to be fulfilled before using preferences during
    * extension initialization.
    *
    * @type {Promise}
@@ skipping 10 matching lines @@
 }
 
 function prefToKey(pref)
 {
   return keyPrefix + pref;
 }
 
 function addPreference(pref)
 {
   Object.defineProperty(Prefs, pref, {
-    get: function()
-    {
-      return (pref in overrides ? overrides : defaults)[pref];
-    },
-    set: function(value)
+    get: () => (pref in overrides ? overrides : defaults)[pref],
+    set: value =>
     {
       let defaultValue = defaults[pref];
 
       if (typeof value != typeof defaultValue)
         throw new Error("Attempt to change preference type");
 
       if (value == defaultValue)
       {
         delete overrides[pref];
         ext.storage.remove(prefToKey(pref));
       }
       else
       {
         overrides[pref] = value;
         ext.storage.set(prefToKey(pref), value);
       }
     },
     enumerable: true
   });
 }
 
 function init()
 {
   let prefs = Object.keys(defaults);
   prefs.forEach(addPreference);
 
   let localLoaded = new Promise(resolve => {
-    ext.storage.get(prefs.map(prefToKey), function(items)
+    ext.storage.get(prefs.map(prefToKey), items =>
     {
       for (let key in items)
         overrides[keyToPref(key)] = items[key];
 
       resolve();
     });
   });
 
   let managedLoaded = new Promise(resolve => {
     if (require("info").platform == "chromium" && "managed" in chrome.storage)
     {
-      chrome.storage.managed.get(null, function(items)
+      chrome.storage.managed.get(null, items =>
       {
         // Opera doesn't support chrome.storage.managed, but instead simply
         // removing the API, Opera sets chrome.runtime.lastError when using it.
         // So we have to retrieve that error, to prevent it from showing up
         // in the console.
         chrome.runtime.lastError;
 
         for (let key in items)
           defaults[key] = items[key];
 
         resolve();
       });
     }
     else
     {
       resolve();
     }
   });
 
   function onLoaded()
   {
-    ext.storage.onChanged.addListener(function(changes)
+    ext.storage.onChanged.addListener(changes =>
     {
       for (let key in changes)
       {
         let pref = keyToPref(key);
         if (pref && pref in defaults)
         {
           let change = changes[key];
           if ("newValue" in change && change.newValue != defaults[pref])
             overrides[pref] = change.newValue;
           else
             delete overrides[pref];
 
           eventEmitter.emit(pref);
         }
       }
     });
   }
 
   Prefs.untilLoaded = Promise.all([localLoaded, managedLoaded]).then(onLoaded);
 }
 
 init();