diff --git a/browser/components/preferences/aboutPermissions.js b/browser/components/preferences/aboutPermissions.js
index 22b527558d09..14a2bf966254 100644
--- a/browser/components/preferences/aboutPermissions.js
+++ b/browser/components/preferences/aboutPermissions.js
@@ -331,8 +331,12 @@ var PermissionDefaults = {
     let value = (aValue != this.DENY);
     Services.prefs.setBoolPref("dom.push.enabled", value);
   },
-  get camera() this.UNKNOWN,
-  get microphone() this.UNKNOWN
+  get camera() {
+    return this.UNKNOWN;
+  },
+  get microphone() {
+    return this.UNKNOWN;
+  }
 };
 
 /**
diff --git a/browser/components/preferences/in-content/applications.js b/browser/components/preferences/in-content/applications.js
index 56e6baa8e5aa..a8ff7cb306b6 100644
--- a/browser/components/preferences/in-content/applications.js
+++ b/browser/components/preferences/in-content/applications.js
@@ -403,7 +403,7 @@ HandlerInfoWrapper.prototype = {
     var disabledPluginTypes = this._getDisabledPluginTypes();
 
     var type = this.type;
-    disabledPluginTypes = disabledPluginTypes.filter(function(v) v != type);
+    disabledPluginTypes = disabledPluginTypes.filter(v => v != type);
 
     this._prefSvc.setCharPref(PREF_DISABLED_PLUGIN_TYPES,
                               disabledPluginTypes.join(","));
@@ -1549,7 +1549,7 @@ var gApplicationsPane = {
       case Ci.nsIHandlerInfo.useHelperApp:
         if (preferredApp)
           menu.selectedItem = 
-            possibleAppMenuItems.filter(function(v) v.handlerApp.equals(preferredApp))[0];
+            possibleAppMenuItems.filter(v => v.handlerApp.equals(preferredApp))[0];
         break;
       case kActionUsePlugin:
         menu.selectedItem = pluginMenuItem;
diff --git a/browser/components/preferences/in-content/main.js b/browser/components/preferences/in-content/main.js
index 26c89d5b43fc..8108d712559a 100644
--- a/browser/components/preferences/in-content/main.js
+++ b/browser/components/preferences/in-content/main.js
@@ -298,7 +298,9 @@ var gMainPane = {
   {
     let homePage = document.getElementById("browser.startup.homepage");
     let tabs = this._getTabsForHomePage();
-    function getTabURI(t) t.linkedBrowser.currentURI.spec;
+    function getTabURI(t) {
+      return t.linkedBrowser.currentURI.spec;
+    }
 
     // FIXME Bug 244192: using dangerous "|" joiner!
     if (tabs.length)
diff --git a/browser/components/preferences/in-content/privacy.js b/browser/components/preferences/in-content/privacy.js
index a10e1c7b2cd4..8a7c6ce92a5a 100644
--- a/browser/components/preferences/in-content/privacy.js
+++ b/browser/components/preferences/in-content/privacy.js
@@ -179,8 +179,7 @@ var gPrivacyPane = {
   initializeHistoryMode: function PPP_initializeHistoryMode()
   {
     let mode;
-    let getVal = function (aPref)
-      document.getElementById(aPref).value;
+    let getVal = aPref => document.getElementById(aPref).value;
 
     if (this._checkDefaultValues(this.prefsForDefault)) {
       if (getVal("browser.privatebrowsing.autostart"))
diff --git a/browser/components/preferences/in-content/search.js b/browser/components/preferences/in-content/search.js
index 9b2df3d62570..23ca3da7d678 100644
--- a/browser/components/preferences/in-content/search.js
+++ b/browser/components/preferences/in-content/search.js
@@ -318,7 +318,7 @@ function EngineStore() {
   this._defaultEngines = Services.search.getDefaultEngines().map(this._cloneEngine, this);
 
   // check if we need to disable the restore defaults button
-  var someHidden = this._defaultEngines.some(function (e) e.hidden);
+  var someHidden = this._defaultEngines.some(e => e.hidden);
   gSearchPane.showRestoreDefaults(someHidden);
 }
 EngineStore.prototype = {
diff --git a/browser/components/preferences/translation.js b/browser/components/preferences/translation.js
index b10baf761e32..cb977fc394fd 100644
--- a/browser/components/preferences/translation.js
+++ b/browser/components/preferences/translation.js
@@ -25,9 +25,15 @@ function Tree(aId, aData)
 }
 
 Tree.prototype = {
-  get boxObject() this._tree.treeBoxObject,
-  get isEmpty() !this._data.length,
-  get hasSelection() this.selection.count > 0,
+  get boxObject() {
+    return this._tree.treeBoxObject;
+  },
+  get isEmpty() {
+    return !this._data.length;
+  },
+  get hasSelection() {
+    return this.selection.count > 0;
+  },
   getSelectedItems: function() {
     let result = [];
 
@@ -43,19 +49,35 @@ Tree.prototype = {
   },
 
   // nsITreeView implementation
-  get rowCount() this._data.length,
-  getCellText: function (aRow, aColumn) this._data[aRow],
-  isSeparator: function(aIndex) false,
-  isSorted: function() false,
-  isContainer: function(aIndex) false,
+  get rowCount() {
+    return this._data.length;
+  },
+  getCellText: function (aRow, aColumn) {
+    return this._data[aRow];
+  },
+  isSeparator: function(aIndex) {
+    return false;
+  },
+  isSorted: function() {
+    return false;
+  },
+  isContainer: function(aIndex) {
+    return false;
+  },
   setTree: function(aTree) {},
   getImageSrc: function(aRow, aColumn) {},
   getProgressMode: function(aRow, aColumn) {},
   getCellValue: function(aRow, aColumn) {},
   cycleHeader: function(column) {},
-  getRowProperties: function(row) "",
-  getColumnProperties: function(column) "",
-  getCellProperties: function(row, column) "",
+  getRowProperties: function(row) {
+    return "";
+  },
+  getColumnProperties: function(column) {
+    return "";
+  },
+  getCellProperties: function(row, column) {
+    return "";
+  },
   QueryInterface: XPCOMUtils.generateQI([Ci.nsITreeView])
 };
 
@@ -66,7 +88,9 @@ function Lang(aCode)
 }
 
 Lang.prototype = {
-  toString: function() this._label
+  toString: function() {
+    return this._label;
+  }
 }
 
 var gTranslationExceptions = {