diff --git a/browser/base/content/test/newtab/head.js b/browser/base/content/test/newtab/head.js
index 58a33e1c6dec..3c469ce8a246 100644
--- a/browser/base/content/test/newtab/head.js
+++ b/browser/base/content/test/newtab/head.js
@@ -51,25 +51,28 @@ Object.keys(requiredSize).forEach(prop => {
     gBrowser.contentWindow[prop] = requiredSize[prop];
   }
 });
-let (screenHeight = {}, screenWidth = {}) {
-  Cc["@mozilla.org/gfx/screenmanager;1"].
-    getService(Ci.nsIScreenManager).
-    primaryScreen.
-    GetAvailRectDisplayPix({}, {}, screenWidth, screenHeight);
-  screenHeight = screenHeight.value;
-  screenWidth = screenWidth.value;
-  if (screenHeight < gBrowser.contentWindow.outerHeight) {
-    info("Warning: Browser outer height is now " +
-         gBrowser.contentWindow.outerHeight + ", which is larger than the " +
-         "available screen height, " + screenHeight +
-         ". That may cause problems.");
-  }
-  if (screenWidth < gBrowser.contentWindow.outerWidth) {
-    info("Warning: Browser outer width is now " +
-         gBrowser.contentWindow.outerWidth + ", which is larger than the " +
-         "available screen width, " + screenWidth +
-         ". That may cause problems.");
-  }
+
+let screenHeight = {};
+let screenWidth = {};
+Cc["@mozilla.org/gfx/screenmanager;1"].
+  getService(Ci.nsIScreenManager).
+  primaryScreen.
+  GetAvailRectDisplayPix({}, {}, screenWidth, screenHeight);
+screenHeight = screenHeight.value;
+screenWidth = screenWidth.value;
+
+if (screenHeight < gBrowser.contentWindow.outerHeight) {
+  info("Warning: Browser outer height is now " +
+       gBrowser.contentWindow.outerHeight + ", which is larger than the " +
+       "available screen height, " + screenHeight +
+       ". That may cause problems.");
+}
+
+if (screenWidth < gBrowser.contentWindow.outerWidth) {
+  info("Warning: Browser outer width is now " +
+       gBrowser.contentWindow.outerWidth + ", which is larger than the " +
+       "available screen width, " + screenWidth +
+       ". That may cause problems.");
 }
 
 registerCleanupFunction(function () {
diff --git a/browser/components/migration/tests/unit/head_migration.js b/browser/components/migration/tests/unit/head_migration.js
index 2f84eac2bb08..1c47a7f94f61 100644
--- a/browser/components/migration/tests/unit/head_migration.js
+++ b/browser/components/migration/tests/unit/head_migration.js
@@ -20,7 +20,7 @@ XPCOMUtils.defineLazyModuleGetter(this, "MigrationUtils",
 let gProfD = do_get_profile();
 
 // Create a fake XULAppInfo to satisfy the eventual needs of the migrators.
-let (XULAppInfo = {
+let XULAppInfo = {
   // nsIXUlAppInfo
   get vendor() "Mozilla",
   get name() "XPCShell",
@@ -48,17 +48,17 @@ let (XULAppInfo = {
       throw Cr.NS_ERROR_NO_INTERFACE;
     return this;
   }
-}) {
-  const CONTRACT_ID = "@mozilla.org/xre/app-info;1";
-  const CID = Components.ID("7685dac8-3637-4660-a544-928c5ec0e714}");
+};
 
-  let registrar = Components.manager.QueryInterface(Ci.nsIComponentRegistrar);
-  registrar.registerFactory(CID, "XULAppInfo", CONTRACT_ID, {
-    createInstance: function (aOuter, aIID) {
-      if (aOuter != null)
-        throw Cr.NS_ERROR_NO_AGGREGATION;
-      return XULAppInfo.QueryInterface(aIID);
-    },
-    QueryInterface: XPCOMUtils.generateQI(Ci.nsIFactory)
-  });
-}
+const CONTRACT_ID = "@mozilla.org/xre/app-info;1";
+const CID = Components.ID("7685dac8-3637-4660-a544-928c5ec0e714}");
+
+let registrar = Components.manager.QueryInterface(Ci.nsIComponentRegistrar);
+registrar.registerFactory(CID, "XULAppInfo", CONTRACT_ID, {
+  createInstance: function (aOuter, aIID) {
+    if (aOuter != null)
+      throw Cr.NS_ERROR_NO_AGGREGATION;
+    return XULAppInfo.QueryInterface(aIID);
+  },
+  QueryInterface: XPCOMUtils.generateQI(Ci.nsIFactory)
+});
diff --git a/browser/components/places/tests/browser/head.js b/browser/components/places/tests/browser/head.js
index 3d1a339ea3a4..6ca611e7adb0 100644
--- a/browser/components/places/tests/browser/head.js
+++ b/browser/components/places/tests/browser/head.js
@@ -11,16 +11,16 @@ XPCOMUtils.defineLazyModuleGetter(this, "PlacesTestUtils",
 
 // We need to cache this before test runs...
 let cachedLeftPaneFolderIdGetter;
-let (getter = PlacesUIUtils.__lookupGetter__("leftPaneFolderId")) {
-  if (!cachedLeftPaneFolderIdGetter && typeof(getter) == "function")
-    cachedLeftPaneFolderIdGetter = getter;
+let getter = PlacesUIUtils.__lookupGetter__("leftPaneFolderId");
+if (!cachedLeftPaneFolderIdGetter && typeof(getter) == "function") {
+  cachedLeftPaneFolderIdGetter = getter;
 }
+
 // ...And restore it when test ends.
 registerCleanupFunction(function(){
-  let (getter = PlacesUIUtils.__lookupGetter__("leftPaneFolderId")) {
-    if (cachedLeftPaneFolderIdGetter && typeof(getter) != "function")
-      PlacesUIUtils.__defineGetter__("leftPaneFolderId",
-                                     cachedLeftPaneFolderIdGetter);
+  let getter = PlacesUIUtils.__lookupGetter__("leftPaneFolderId");
+  if (cachedLeftPaneFolderIdGetter && typeof(getter) != "function") {
+    PlacesUIUtils.__defineGetter__("leftPaneFolderId", cachedLeftPaneFolderIdGetter);
   }
 });
 
diff --git a/browser/components/places/tests/unit/head_bookmarks.js b/browser/components/places/tests/unit/head_bookmarks.js
index c8cf9068ab98..a45f4d1428c1 100644
--- a/browser/components/places/tests/unit/head_bookmarks.js
+++ b/browser/components/places/tests/unit/head_bookmarks.js
@@ -28,7 +28,7 @@ XPCOMUtils.defineLazyGetter(this, "PlacesUIUtils", function() {
 const ORGANIZER_FOLDER_ANNO = "PlacesOrganizer/OrganizerFolder";
 const ORGANIZER_QUERY_ANNO = "PlacesOrganizer/OrganizerQuery";
 
-// Needed by some test that relies on having an app  registered.
+// Needed by some test that relies on having an app registered.
 let XULAppInfo = {
   vendor: "Mozilla",
   name: "PlacesTest",
diff --git a/browser/components/preferences/applications.js b/browser/components/preferences/applications.js
index 7d808b1b8331..3334fbaf7ab1 100644
--- a/browser/components/preferences/applications.js
+++ b/browser/components/preferences/applications.js
@@ -1841,10 +1841,9 @@ var gApplicationsPane = {
         return this._getIconURLForSystemDefault(aHandlerInfo);
 
       case Ci.nsIHandlerInfo.useHelperApp:
-        let (preferredApp = aHandlerInfo.preferredApplicationHandler) {
-          if (this.isValidHandlerApp(preferredApp))
-            return this._getIconURLForHandlerApp(preferredApp);
-        }
+        let preferredApp = aHandlerInfo.preferredApplicationHandler;
+        if (this.isValidHandlerApp(preferredApp))
+          return this._getIconURLForHandlerApp(preferredApp);
         break;
 
       // This should never happen, but if preferredAction is set to some weird
diff --git a/browser/components/sessionstore/test/browser_506482.js b/browser/components/sessionstore/test/browser_506482.js
index 77f4084c7b09..6e5bd83bdbd4 100644
--- a/browser/components/sessionstore/test/browser_506482.js
+++ b/browser/components/sessionstore/test/browser_506482.js
@@ -26,11 +26,10 @@ function test() {
   }
 
   // delete existing sessionstore.js, to make sure we're not reading
-  // the mtime of an old one initialy
-  let (sessionStoreJS = getSessionstoreFile()) {
-    if (sessionStoreJS.exists())
-      sessionStoreJS.remove(false);
-  }
+  // the mtime of an old one initially.
+  let sessionStoreJS = getSessionstoreFile();
+  if (sessionStoreJS.exists())
+    sessionStoreJS.remove(false);
 
   // test content URL
   const TEST_URL = "data:text/html;charset=utf-8,"
diff --git a/browser/components/sessionstore/test/unit/test_backup_once.js b/browser/components/sessionstore/test/unit/test_backup_once.js
index 75d327dafa7d..aac6dde1d11e 100644
--- a/browser/components/sessionstore/test/unit/test_backup_once.js
+++ b/browser/components/sessionstore/test/unit/test_backup_once.js
@@ -13,7 +13,7 @@ let Paths;
 let SessionFile;
 
 // We need a XULAppInfo to initialize SessionFile
-let (XULAppInfo = {
+let XULAppInfo = {
   vendor: "Mozilla",
   name: "SessionRestoreTest",
   ID: "{230de50e-4cd1-11dc-8314-0800200c9a66}",
@@ -30,20 +30,20 @@ let (XULAppInfo = {
     Ci.nsIXULAppInfo,
     Ci.nsIXULRuntime,
   ])
-}) {
-  let XULAppInfoFactory = {
-    createInstance: function (outer, iid) {
-      if (outer != null)
-        throw Cr.NS_ERROR_NO_AGGREGATION;
-      return XULAppInfo.QueryInterface(iid);
-    }
-  };
-  let registrar = Components.manager.QueryInterface(Ci.nsIComponentRegistrar);
-  registrar.registerFactory(Components.ID("{fbfae60b-64a4-44ef-a911-08ceb70b9f31}"),
-                            "XULAppInfo", "@mozilla.org/xre/app-info;1",
-                            XULAppInfoFactory);
 };
 
+let XULAppInfoFactory = {
+  createInstance: function (outer, iid) {
+    if (outer != null)
+      throw Cr.NS_ERROR_NO_AGGREGATION;
+    return XULAppInfo.QueryInterface(iid);
+  }
+};
+let registrar = Components.manager.QueryInterface(Ci.nsIComponentRegistrar);
+registrar.registerFactory(Components.ID("{fbfae60b-64a4-44ef-a911-08ceb70b9f31}"),
+                          "XULAppInfo", "@mozilla.org/xre/app-info;1",
+                          XULAppInfoFactory);
+
 function run_test() {
   run_next_test();
 }