diff --git a/services/cloudsync/CloudSyncBookmarks.jsm b/services/cloudsync/CloudSyncBookmarks.jsm
index fba7f53f7a6..c3c8efbd9b9 100644
--- a/services/cloudsync/CloudSyncBookmarks.jsm
+++ b/services/cloudsync/CloudSyncBookmarks.jsm
@@ -554,7 +554,7 @@ var RootFolder = function (rootId, rootName) {
         }
       }
 
-      for each (let item in items) {
+      for (let item of items) {
         if (!item || 'object' !== typeof(item)) {
           continue;
         }
@@ -570,7 +570,7 @@ var RootFolder = function (rootId, rootName) {
       let newFolderGuids = Object.keys(newFolders);
       let newFolderRoots = [];
 
-      for each (let guid in newFolderGuids) {
+      for (let guid of newFolderGuids) {
         let item = newFolders[guid];
         if (item.parent && newFolderGuids.indexOf(item.parent) >= 0) {
           let parent = newFolders[item.parent];
@@ -581,7 +581,7 @@ var RootFolder = function (rootId, rootName) {
       };
 
       let promises = [];
-      for each (let guid in newFolderRoots) {
+      for (let guid of newFolderRoots) {
         let root = newFolders[guid];
         let promise = Promise.resolve();
         promise = promise.then(
@@ -611,15 +611,15 @@ var RootFolder = function (rootId, rootName) {
     let processItems = function () {
       let promises = [];
 
-      for each (let item in newItems) {
+      for (let item of newItems) {
         promises.push(_createItem(item));
       }
 
-      for each (let item in updatedItems) {
+      for (let item of updatedItems) {
         promises.push(_updateItem(item));
       }
 
-      for each (let item in deletedItems) {
+      for (let item of deletedItems) {
         _deleteItem(item);
       }
 
diff --git a/services/cloudsync/CloudSyncEventSource.jsm b/services/cloudsync/CloudSyncEventSource.jsm
index c17b60c594b..edb9c426b29 100644
--- a/services/cloudsync/CloudSyncEventSource.jsm
+++ b/services/cloudsync/CloudSyncEventSource.jsm
@@ -8,7 +8,7 @@ Components.utils.import("resource://services-common/utils.js");
 
 var EventSource = function (types, suspendFunc, resumeFunc) {
   this.listeners = new Map();
-  for each (let type in types) {
+  for (let type of types) {
     this.listeners.set(type, new Set());
   }
 
diff --git a/services/cloudsync/CloudSyncPlacesWrapper.jsm b/services/cloudsync/CloudSyncPlacesWrapper.jsm
index 9aba94e9d43..dd8c5c52eb4 100644
--- a/services/cloudsync/CloudSyncPlacesWrapper.jsm
+++ b/services/cloudsync/CloudSyncPlacesWrapper.jsm
@@ -140,7 +140,7 @@ PlacesWrapper.prototype = {
       function (items) {
         let previousIds = folderCache.getChildren(folder);
         let currentIds = new Set();
-        for each (let item in items) {
+        for (let item of items) {
           currentIds.add(item.id);
         }
         let newIds = new Set();
@@ -188,7 +188,7 @@ PlacesWrapper.prototype = {
     this.asyncQuery(query, ["item_id"])
         .then(function (items) {
                 let results = [];
-                for each(let item in items) {
+                for (let item of items) {
                   results.push(item.item_id);
                 }
                 deferred.resolve(results);
@@ -211,7 +211,7 @@ PlacesWrapper.prototype = {
     this.asyncQuery(query, ["name", "content"])
         .then(function (results) {
                 let annos = {};
-                for each(let result in results) {
+                for (let result of results) {
                   annos[result.name] = result.content;
                 }
                 deferred.resolve(annos);
@@ -347,7 +347,7 @@ PlacesWrapper.prototype = {
         let row;
         while ((row = results.getNextRow()) != null) {
           let item = {};
-          for each (let name in names) {
+          for (let name of names) {
             item[name] = row.getResultByName(name);
           }
           this.results.push(item);
diff --git a/services/cloudsync/CloudSyncTabs.jsm b/services/cloudsync/CloudSyncTabs.jsm
index acebeba2114..7debc26782b 100644
--- a/services/cloudsync/CloudSyncTabs.jsm
+++ b/services/cloudsync/CloudSyncTabs.jsm
@@ -87,7 +87,7 @@ TabCache.prototype = {
       this.clients.set(cRecord.id, cRecord);
     }
 
-    for each (let tab in tabs) {
+    for (let tab of tabs) {
       if (!tab || 'object' !== typeof(tab)) {
         continue;
       }
@@ -158,7 +158,7 @@ this.Tabs = function () {
   };
 
   let registerListenersForWindow = function (window) {
-    for each (let topic in topics) {
+    for (let topic of topics) {
       window.addEventListener(topic, update, false);
     }
     window.addEventListener("unload", unregisterListeners, false);
@@ -166,7 +166,7 @@ this.Tabs = function () {
 
   let unregisterListenersForWindow = function (window) {
     window.removeEventListener("unload", unregisterListeners, false);
-    for each (let topic in topics) {
+    for (let topic of topics) {
       window.removeEventListener(topic, update, false);
     }
   };
diff --git a/services/common/async.js b/services/common/async.js
index 6ba0de2a52a..680f5e45ff1 100644
--- a/services/common/async.js
+++ b/services/common/async.js
@@ -177,7 +177,7 @@ this.Async = {
       let row;
       while ((row = results.getNextRow()) != null) {
         let item = {};
-        for each (let name in this.names) {
+        for (let name of this.names) {
           item[name] = row.getResultByName(name);
         }
         this.results.push(item);
diff --git a/services/common/modules-testing/storageserver.js b/services/common/modules-testing/storageserver.js
index c876b5aba22..94c787c4e2a 100644
--- a/services/common/modules-testing/storageserver.js
+++ b/services/common/modules-testing/storageserver.js
@@ -102,7 +102,7 @@ ServerBSO.prototype = {
   toJSON: function toJSON() {
     let obj = {};
 
-    for each (let key in this.FIELDS) {
+    for (let key of this.FIELDS) {
       if (this[key] !== undefined) {
         obj[key] = this[key];
       }
@@ -306,7 +306,7 @@ StorageServerCollection.prototype = {
 
   get totalPayloadSize() {
     let size = 0;
-    for each (let bso in this.bsos()) {
+    for (let bso of this.bsos()) {
       size += bso.payload.length;
     }
 
@@ -441,7 +441,8 @@ StorageServerCollection.prototype = {
 
   get: function get(options) {
     let data = [];
-    for each (let bso in this._bsos) {
+    for (let id in this._bsos) {
+      let bso = this._bsos[id];
       if (!bso.modified) {
         continue;
       }
@@ -504,7 +505,7 @@ StorageServerCollection.prototype = {
 
     // This will count records where we have an existing ServerBSO
     // registered with us as successful and all other records as failed.
-    for each (let record in input) {
+    for (let record of input) {
       count += 1;
       if (count > this.BATCH_MAX_COUNT) {
         failed[record.id] = "Max record count exceeded.";
@@ -602,7 +603,7 @@ StorageServerCollection.prototype = {
   parseOptions: function parseOptions(request) {
     let options = {};
 
-    for each (let chunk in request.queryString.split("&")) {
+    for (let chunk of request.queryString.split("&")) {
       if (!chunk) {
         continue;
       }
@@ -656,7 +657,7 @@ StorageServerCollection.prototype = {
       let requestModified = parseInt(request.getHeader("x-if-modified-since"),
                                      10);
       let newestBSO = 0;
-      for each (let bso in data) {
+      for (let bso of data) {
         if (bso.modified > newestBSO) {
           newestBSO = bso.modified;
         }
@@ -746,7 +747,7 @@ StorageServerCollection.prototype = {
         return sendMozSvcError(request, response, "8");
       }
     } else if (inputMediaType == "application/newlines") {
-      for each (let line in inputBody.split("\n")) {
+      for (let line of inputBody.split("\n")) {
         let record;
         try {
           record = JSON.parse(line);
@@ -1078,7 +1079,8 @@ StorageServer.prototype = {
       throw new Error("Unknown user.");
     }
     let userCollections = this.users[username].collections;
-    for each (let [name, coll] in Iterator(userCollections)) {
+    for (let name in userCollections) {
+      let coll = userCollections[name];
       this._log.trace("Bulk deleting " + name + " for " + username + "...");
       coll.delete({});
     }
@@ -1099,7 +1101,8 @@ StorageServer.prototype = {
   newestCollectionTimestamp: function newestCollectionTimestamp(username) {
     let collections = this.users[username].collections;
     let newest = 0;
-    for each (let collection in collections) {
+    for (let name in collections) {
+      let collection = collections[name];
       if (collection.timestamp > newest) {
         newest = collection.timestamp;
       }
@@ -1149,7 +1152,9 @@ StorageServer.prototype = {
 
   infoQuota: function infoQuota(username) {
     let total = 0;
-    for each (let value in this.infoUsage(username)) {
+    let usage = this.infoUsage(username);
+    for (let key in usage) {
+      let value = usage[key];
       total += value;
     }
 
@@ -1191,9 +1196,11 @@ StorageServer.prototype = {
   _pruneExpired: function _pruneExpired() {
     let now = Date.now();
 
-    for each (let user in this.users) {
-      for each (let collection in user.collections) {
-        for each (let bso in collection.bsos()) {
+    for (let username in this.users) {
+      let user = this.users[username];
+      for (let name in user.collections) {
+        let collection = user.collections[name];
+        for (let bso of collection.bsos()) {
           // ttl === 0 is a special case, so we can't simply !ttl.
           if (typeof(bso.ttl) != "number") {
             continue;
@@ -1240,7 +1247,11 @@ StorageServer.prototype = {
   respond: function respond(req, resp, code, status, body, headers, timestamp) {
     this._log.info("Response: " + code + " " + status);
     resp.setStatusLine(req.httpVersion, code, status);
-    for each (let [header, value] in Iterator(headers || this.defaultHeaders)) {
+    if (!headers) {
+      headers = this.defaultHeaders;
+    }
+    for (let header in headers) {
+      let value = headers[header];
       resp.setHeader(header, value, false);
     }
 
diff --git a/services/common/stringbundle.js b/services/common/stringbundle.js
index 4e6a34c0540..a07fa4831ed 100644
--- a/services/common/stringbundle.js
+++ b/services/common/stringbundle.js
@@ -24,7 +24,7 @@ var {classes: Cc, interfaces: Ci, results: Cr, utils: Cu} = Components;
  *     new StringBundle("chrome://example/locale/strings.properties");
  *   let foo = strings.get("foo");
  *   let barFormatted = strings.get("bar", [arg1, arg2]);
- *   for each (let string in strings.getAll())
+ *   for (let string of strings.getAll())
  *     dump (string.key + " = " + string.value + "\n");
  *
  * @param url {String}
diff --git a/services/common/tests/mach_commands.py b/services/common/tests/mach_commands.py
index 97977cafe61..6777b81e4ce 100644
--- a/services/common/tests/mach_commands.py
+++ b/services/common/tests/mach_commands.py
@@ -87,7 +87,7 @@ class SyncTestCommands(MachCommandBase):
             '-e', 'const SERVER_PORT = "%s";' % port,
             '-e', 'const INCLUDE_FILES = [%s];' % ', '.join(head_paths),
             '-e', '_register_protocol_handlers();',
-            '-e', 'for each (let name in INCLUDE_FILES) load(name);',
+            '-e', 'for (let name of INCLUDE_FILES) load(name);',
             '-e', '_fakeIdleService.activate();',
             '-f', js_file
             ]
diff --git a/services/common/tests/unit/head_global.js b/services/common/tests/unit/head_global.js
index d1006ab8b50..b278780bb2c 100644
--- a/services/common/tests/unit/head_global.js
+++ b/services/common/tests/unit/head_global.js
@@ -42,7 +42,7 @@ function addResourceAlias() {
                   .QueryInterface(Ci.nsIResProtocolHandler);
 
   let modules = ["common", "crypto"];
-  for each (let module in modules) {
+  for (let module of modules) {
     let uri = Services.io.newURI("resource://gre/modules/services-" + module + "/",
                                  null, null);
     handler.setSubstitution("services-" + module, uri);
diff --git a/services/common/tests/unit/test_load_modules.js b/services/common/tests/unit/test_load_modules.js
index 1e159dfebcb..b549c93ef09 100644
--- a/services/common/tests/unit/test_load_modules.js
+++ b/services/common/tests/unit/test_load_modules.js
@@ -34,7 +34,7 @@ const non_android_healthreport_test_modules = [
 ];
 
 function expectImportsToSucceed(mm, base=MODULE_BASE) {
-  for each (let m in mm) {
+  for (let m of mm) {
     let resource = base + m;
     let succeeded = false;
     try {
@@ -49,7 +49,7 @@ function expectImportsToSucceed(mm, base=MODULE_BASE) {
 }
 
 function expectImportsToFail(mm, base=MODULE_BASE) {
-  for each (let m in mm) {
+  for (let m of mm) {
     let resource = base + m;
     let succeeded = false;
     try {
diff --git a/services/common/tests/unit/test_tokenserverclient.js b/services/common/tests/unit/test_tokenserverclient.js
index 65ae471eb51..b24d2fbec4f 100644
--- a/services/common/tests/unit/test_tokenserverclient.js
+++ b/services/common/tests/unit/test_tokenserverclient.js
@@ -60,7 +60,7 @@ add_test(function test_invalid_arguments() {
     ["http://example.com/", "assertion", null]
   ];
 
-  for each (let arg in args) {
+  for (let arg of args) {
     try {
       let client = new TokenServerClient();
       client.getTokenFromBrowserIDAssertion(arg[0], arg[1], arg[2]);
diff --git a/services/common/utils.js b/services/common/utils.js
index 69571837f60..16a18a98a36 100644
--- a/services/common/utils.js
+++ b/services/common/utils.js
@@ -205,16 +205,15 @@ this.CommonUtils = {
   },
 
   byteArrayToString: function byteArrayToString(bytes) {
-    return [String.fromCharCode(byte) for each (byte in bytes)].join("");
+    return bytes.map(byte => String.fromCharCode(byte)).join("");
   },
 
   stringToByteArray: function stringToByteArray(bytesString) {
-    return [String.charCodeAt(byte) for each (byte in bytesString)];
+    return Array.prototype.slice.call(bytesString).map(c => c.charCodeAt(0));
   },
 
   bytesAsHex: function bytesAsHex(bytes) {
-    return [("0" + bytes.charCodeAt(byte).toString(16)).slice(-2)
-      for (byte in bytes)].join("");
+    return Array.prototype.slice.call(bytes).map(c => ("0" + c.charCodeAt(0).toString(16)).slice(-2)).join("");
   },
 
   stringAsHex: function stringAsHex(str) {
@@ -256,7 +255,7 @@ this.CommonUtils = {
     // is turned into 8 characters from the 32 character base.
     let ret = "";
     for (let i = 0; i < bytes.length; i += 5) {
-      let c = [byte.charCodeAt() for each (byte in bytes.slice(i, i + 5))];
+      let c = Array.prototype.slice.call(bytes.slice(i, i + 5)).map(byte => byte.charCodeAt(0));
       ret += key[c[0] >> 3]
            + key[((c[0] << 2) & 0x1f) | (c[1] >> 6)]
            + key[(c[1] >> 1) & 0x1f]
diff --git a/services/crypto/modules/utils.js b/services/crypto/modules/utils.js
index ca4da86477a..0c727c2c507 100644
--- a/services/crypto/modules/utils.js
+++ b/services/crypto/modules/utils.js
@@ -56,7 +56,7 @@ this.CryptoUtils = {
    */
   digestBytes: function digestBytes(message, hasher) {
     // No UTF-8 encoding for you, sunshine.
-    let bytes = [b.charCodeAt() for each (b in message)];
+    let bytes = Array.prototype.slice.call(message).map(b => b.charCodeAt(0));
     hasher.update(bytes, bytes.length);
     let result = hasher.finish(false);
     if (hasher instanceof Ci.nsICryptoHMAC) {
diff --git a/services/crypto/tests/unit/test_load_modules.js b/services/crypto/tests/unit/test_load_modules.js
index 2b9a1485643..50f5d709c5b 100644
--- a/services/crypto/tests/unit/test_load_modules.js
+++ b/services/crypto/tests/unit/test_load_modules.js
@@ -7,7 +7,7 @@ const modules = [
 ];
 
 function run_test() {
-  for each (let m in modules) {
+  for (let m of modules) {
     let resource = "resource://services-crypto/" + m;
     _("Attempting to import: " + resource);
     Components.utils.import(resource, {});
diff --git a/services/metrics/providermanager.jsm b/services/metrics/providermanager.jsm
index 90be563a97e..cf26d444b29 100644
--- a/services/metrics/providermanager.jsm
+++ b/services/metrics/providermanager.jsm
@@ -282,7 +282,8 @@ this.ProviderManager.prototype = Object.freeze({
         }
       }
 
-      for each (let providerType in this._pullOnlyProviders) {
+      for (let name in this._pullOnlyProviders) {
+        let providerType = this._pullOnlyProviders[name];
         // Short-circuit if we're no longer registering.
         if (this._pullOnlyProvidersState != this.PULL_ONLY_REGISTERING) {
           this._log.debug("Aborting pull-only provider registration.");
diff --git a/services/sync/modules/addonsreconciler.js b/services/sync/modules/addonsreconciler.js
index 2c16e2e81e6..58605f55d56 100644
--- a/services/sync/modules/addonsreconciler.js
+++ b/services/sync/modules/addonsreconciler.js
@@ -218,11 +218,12 @@ AddonsReconciler.prototype = {
       }
 
       this._addons = json.addons;
-      for each (let record in this._addons) {
+      for (let id in this._addons) {
+        let record = this._addons[id];
         record.modified = new Date(record.modified);
       }
 
-      for each (let [time, change, id] in json.changes) {
+      for (let [time, change, id] of json.changes) {
         this._changes.push([new Date(time), change, id]);
       }
 
@@ -258,7 +259,7 @@ AddonsReconciler.prototype = {
       }
     }
 
-    for each (let [time, change, id] in this._changes) {
+    for (let [time, change, id] of this._changes) {
       state.changes.push([time.getTime(), change, id]);
     }
 
@@ -350,7 +351,7 @@ AddonsReconciler.prototype = {
     AddonManager.getAllAddons(function (addons) {
       let ids = {};
 
-      for each (let addon in addons) {
+      for (let addon of addons) {
         ids[addon.id] = true;
         this.rectifyStateFromAddon(addon);
       }
@@ -373,7 +374,7 @@ AddonsReconciler.prototype = {
         }
 
         let installFound = false;
-        for each (let install in installs) {
+        for (let install of installs) {
           if (install.addon && install.addon.id == id &&
               install.state == AddonManager.STATE_INSTALLED) {
 
@@ -483,7 +484,7 @@ AddonsReconciler.prototype = {
     this._log.info("Change recorded for " + state.id);
     this._changes.push([date, change, state.id]);
 
-    for each (let listener in this._listeners) {
+    for (let listener of this._listeners) {
       try {
         listener.changeListener.call(listener, date, change, state);
       } catch (ex) {
@@ -554,7 +555,8 @@ AddonsReconciler.prototype = {
    * @return Object on success on null on failure.
    */
   getAddonStateFromSyncGUID: function getAddonStateFromSyncGUID(guid) {
-    for each (let addon in this.addons) {
+    for (let id in this.addons) {
+      let addon = this.addons[id];
       if (addon.guid == guid) {
         return addon;
       }
diff --git a/services/sync/modules/addonutils.js b/services/sync/modules/addonutils.js
index 63d9578d038..3a29901c13b 100644
--- a/services/sync/modules/addonutils.js
+++ b/services/sync/modules/addonutils.js
@@ -248,7 +248,7 @@ AddonUtilsInternal.prototype = {
     }
 
     let ids = [];
-    for each (let addon in installs) {
+    for (let addon of installs) {
       ids.push(addon.id);
     }
 
@@ -298,7 +298,7 @@ AddonUtilsInternal.prototype = {
         // server-side metrics aren't skewed (bug 708134). The server should
         // ideally send proper URLs, but this solution was deemed too
         // complicated at the time the functionality was implemented.
-        for each (let addon in addons) {
+        for (let addon of addons) {
           // sourceURI presence isn't enforced by AddonRepository. So, we skip
           // add-ons without a sourceURI.
           if (!addon.sourceURI) {
@@ -342,9 +342,9 @@ AddonUtilsInternal.prototype = {
 
         // Start all the installs asynchronously. They will report back to us
         // as they finish, eventually triggering the global callback.
-        for each (let addon in toInstall) {
+        for (let addon of toInstall) {
           let options = {};
-          for each (let install in installs) {
+          for (let install of installs) {
             if (install.id == addon.id) {
               options = install;
               break;
diff --git a/services/sync/modules/engines.js b/services/sync/modules/engines.js
index 04e91e7b18c..21dee0324d2 100644
--- a/services/sync/modules/engines.js
+++ b/services/sync/modules/engines.js
@@ -299,7 +299,7 @@ Store.prototype = {
    */
   applyIncomingBatch: function (records) {
     let failed = [];
-    for each (let record in records) {
+    for (let record of records) {
       try {
         this.applyIncoming(record);
       } catch (ex if (ex.code == Engine.prototype.eEngineAbortApplyIncoming)) {
@@ -497,7 +497,7 @@ EngineManager.prototype = {
   },
 
   get enabledEngineNames() {
-    return [e.name for each (e in this.getEnabled())];
+    return this.getEnabled().map(e => e.name);
   },
 
   persistDeclined: function () {
@@ -1464,14 +1464,15 @@ SyncEngine.prototype = {
                           + failed_ids.join(", "));
 
         // Clear successfully uploaded objects.
-        for each (let id in resp.obj.success) {
+        for (let key in resp.obj.success) {
+          let id = resp.obj.success[key];
           delete this._modified[id];
         }
 
         up.clearRecords();
       });
 
-      for each (let id in modifiedIDs) {
+      for (let id of modifiedIDs) {
         try {
           let out = this._createRecord(id);
           if (this._log.level <= Log.Level.Trace)
diff --git a/services/sync/modules/engines/addons.js b/services/sync/modules/engines/addons.js
index 5bf818db708..eabc66a86ae 100644
--- a/services/sync/modules/engines/addons.js
+++ b/services/sync/modules/engines/addons.js
@@ -160,7 +160,7 @@ AddonsEngine.prototype = {
     // we assume this function is only called from within a sync.
     let reconcilerChanges = this._reconciler.getChangesSinceDate(lastSyncDate);
     let addons = this._reconciler.addons;
-    for each (let change in reconcilerChanges) {
+    for (let change of reconcilerChanges) {
       let changeTime = change[0];
       let id = change[2];
 
@@ -299,7 +299,7 @@ AddonsStore.prototype = {
     let results = cb.wait();
 
     let addon;
-    for each (let a in results.addons) {
+    for (let a of results.addons) {
       if (a.id == record.addonID) {
         addon = a;
         break;
@@ -443,7 +443,8 @@ AddonsStore.prototype = {
     let ids = {};
 
     let addons = this.reconciler.addons;
-    for each (let addon in addons) {
+    for (let id in addons) {
+      let addon = addons[id];
       if (this.isAddonSyncable(addon)) {
         ids[addon.guid] = true;
       }
diff --git a/services/sync/modules/engines/bookmarks.js b/services/sync/modules/engines/bookmarks.js
index 81b96344d39..d59f3b26da7 100644
--- a/services/sync/modules/engines/bookmarks.js
+++ b/services/sync/modules/engines/bookmarks.js
@@ -179,7 +179,7 @@ var kSpecialIds = {
 
   // Don't bother creating mobile: if it doesn't exist, this ID can't be it!
   specialGUIDForId: function specialGUIDForId(id) {
-    for each (let guid in this.guids)
+    for (let guid of this.guids)
       if (this.specialIdForGUID(guid, false) == id)
         return guid;
     return null;
@@ -507,7 +507,8 @@ function BookmarksStore(name, engine) {
 
   // Explicitly nullify our references to our cached services so we don't leak
   Svc.Obs.add("places-shutdown", function() {
-    for each (let [query, stmt] in Iterator(this._stmts)) {
+    for (let query in this._stmts) {
+      let stmt = this._stmts[query];
       stmt.finalize();
     }
     this._stmts = {};
@@ -564,7 +565,7 @@ BookmarksStore.prototype = {
           this._log.debug("Tag query folder: " + tag + " = " + child.itemId);
           
           this._log.trace("Replacing folders in: " + uri);
-          for each (let q in queriesRef.value)
+          for (let q of queriesRef.value)
             q.setFolders([child.itemId], 1);
           
           record.bmkUri = PlacesUtils.history.queriesToQueryString(
@@ -1361,7 +1362,7 @@ BookmarksStore.prototype = {
     if (kSpecialIds.findMobileRoot(false)) {
       items["mobile"] = true;
     }
-    for each (let guid in kSpecialIds.guids) {
+    for (let guid of kSpecialIds.guids) {
       if (guid != "places" && guid != "tags")
         this._getChildren(guid, items);
     }
@@ -1373,7 +1374,7 @@ BookmarksStore.prototype = {
     Task.spawn(function() {
       // Save a backup before clearing out all bookmarks.
       yield PlacesBackups.create(null, true);
-      for each (let guid in kSpecialIds.guids)
+      for (let guid of kSpecialIds.guids)
         if (guid != "places") {
           let id = kSpecialIds.specialIdForGUID(guid);
           if (id)
diff --git a/services/sync/modules/engines/clients.js b/services/sync/modules/engines/clients.js
index 05e0974c443..96b1766b8a3 100644
--- a/services/sync/modules/engines/clients.js
+++ b/services/sync/modules/engines/clients.js
@@ -68,7 +68,8 @@ ClientEngine.prototype = {
       numClients: 1,
     };
 
-    for each (let {name, type} in this._store._remoteClients) {
+    for (let id in this._store._remoteClients) {
+      let {name, type} = this._store._remoteClients[id];
       stats.hasMobile = stats.hasMobile || type == "mobile";
       stats.names.push(name);
       stats.numClients++;
@@ -87,7 +88,8 @@ ClientEngine.prototype = {
 
     counts.set(this.localType, 1);
 
-    for each (let record in this._store._remoteClients) {
+    for (let id in this._store._remoteClients) {
+      let record = this._store._remoteClients[id];
       let type = record.type;
       if (!counts.has(type)) {
         counts.set(type, 0);
@@ -258,7 +260,11 @@ ClientEngine.prototype = {
       this.clearCommands();
 
       // Process each command in order.
-      for each (let {command, args} in commands) {
+      if (!commands) {
+        return true;
+      }
+      for (let key in commands) {
+        let {command, args} = commands[key];
         this._log.debug("Processing command: " + command + "(" + args + ")");
 
         let engines = [args[0]];
diff --git a/services/sync/modules/engines/history.js b/services/sync/modules/engines/history.js
index 3735f6262de..62c999533d9 100644
--- a/services/sync/modules/engines/history.js
+++ b/services/sync/modules/engines/history.js
@@ -70,7 +70,8 @@ function HistoryStore(name, engine) {
 
   // Explicitly nullify our references to our cached services so we don't leak
   Svc.Obs.add("places-shutdown", function() {
-    for each ([query, stmt] in Iterator(this._stmts)) {
+    for (let query in this._stmts) {
+      let stmt = this._stmts;
       stmt.finalize();
     }
     this._stmts = {};
diff --git a/services/sync/modules/engines/passwords.js b/services/sync/modules/engines/passwords.js
index 9ebbb4d7b5b..b570ab654f3 100644
--- a/services/sync/modules/engines/passwords.js
+++ b/services/sync/modules/engines/passwords.js
@@ -85,7 +85,7 @@ PasswordEngine.prototype = {
     this._store._sleep(0); // Yield back to main thread after synchronous operation.
 
     // Look for existing logins that match the hostname, but ignore the password.
-    for each (let local in logins) {
+    for (let local of logins) {
       if (login.matches(local, true) && local instanceof Ci.nsILoginMetaInfo) {
         return local.guid;
       }
diff --git a/services/sync/modules/engines/prefs.js b/services/sync/modules/engines/prefs.js
index 63174083e3f..e801f0147df 100644
--- a/services/sync/modules/engines/prefs.js
+++ b/services/sync/modules/engines/prefs.js
@@ -101,7 +101,7 @@ PrefStore.prototype = {
 
   _getAllPrefs: function () {
     let values = {};
-    for each (let pref in this._getSyncPrefs()) {
+    for (let pref of this._getSyncPrefs()) {
       if (this._isSynced(pref)) {
         // Missing prefs get the null value.
         values[pref] = this._prefs.get(pref, null);
diff --git a/services/sync/modules/engines/tabs.js b/services/sync/modules/engines/tabs.js
index 5bd775fa8ac..167faf62563 100644
--- a/services/sync/modules/engines/tabs.js
+++ b/services/sync/modules/engines/tabs.js
@@ -302,7 +302,7 @@ TabTracker.prototype = {
 
   _registerListenersForWindow: function (window) {
     this._log.trace("Registering tab listeners in window");
-    for each (let topic in this._topics) {
+    for (let topic of this._topics) {
       window.addEventListener(topic, this.onTab, false);
     }
     window.addEventListener("unload", this._unregisterListeners, false);
@@ -315,7 +315,7 @@ TabTracker.prototype = {
   _unregisterListenersForWindow: function (window) {
     this._log.trace("Removing tab listeners in window");
     window.removeEventListener("unload", this._unregisterListeners, false);
-    for each (let topic in this._topics) {
+    for (let topic of this._topics) {
       window.removeEventListener(topic, this.onTab, false);
     }
   },
diff --git a/services/sync/modules/identity.js b/services/sync/modules/identity.js
index b1f26ac997e..66c1e4b6b98 100644
--- a/services/sync/modules/identity.js
+++ b/services/sync/modules/identity.js
@@ -195,7 +195,7 @@ IdentityManager.prototype = {
         return null;
       }
 
-      for each (let login in this._getLogins(PWDMGR_PASSWORD_REALM)) {
+      for (let login of this._getLogins(PWDMGR_PASSWORD_REALM)) {
         if (login.username.toLowerCase() == username) {
           // It should already be UTF-8 encoded, but we don't take any chances.
           this._basicPassword = Utils.encodeUTF8(login.password);
@@ -249,7 +249,7 @@ IdentityManager.prototype = {
         return null;
       }
 
-      for each (let login in this._getLogins(PWDMGR_PASSPHRASE_REALM)) {
+      for (let login of this._getLogins(PWDMGR_PASSPHRASE_REALM)) {
         if (login.username.toLowerCase() == username) {
           this._syncKey = login.password;
         }
@@ -400,7 +400,7 @@ IdentityManager.prototype = {
         this._setLogin(PWDMGR_PASSWORD_REALM, this.username,
                        this._basicPassword);
       } else {
-        for each (let login in this._getLogins(PWDMGR_PASSWORD_REALM)) {
+        for (let login of this._getLogins(PWDMGR_PASSWORD_REALM)) {
           Services.logins.removeLogin(login);
         }
       }
@@ -412,7 +412,7 @@ IdentityManager.prototype = {
       if (this._syncKey) {
         this._setLogin(PWDMGR_PASSPHRASE_REALM, this.username, this._syncKey);
       } else {
-        for each (let login in this._getLogins(PWDMGR_PASSPHRASE_REALM)) {
+        for (let login of this._getLogins(PWDMGR_PASSPHRASE_REALM)) {
           Services.logins.removeLogin(login);
         }
       }
@@ -466,7 +466,7 @@ IdentityManager.prototype = {
    */
   _setLogin: function _setLogin(realm, username, password) {
     let exists = false;
-    for each (let login in this._getLogins(realm)) {
+    for (let login of this._getLogins(realm)) {
       if (login.username == username && login.password == password) {
         exists = true;
       } else {
@@ -502,7 +502,7 @@ IdentityManager.prototype = {
   deleteSyncCredentials: function deleteSyncCredentials() {
     for (let host of this._getSyncCredentialsHosts()) {
       let logins = Services.logins.findLogins({}, host, "", "");
-      for each (let login in logins) {
+      for (let login of logins) {
         Services.logins.removeLogin(login);
       }
     }
diff --git a/services/sync/modules/jpakeclient.js b/services/sync/modules/jpakeclient.js
index 51099da08c7..625dc91b6c3 100644
--- a/services/sync/modules/jpakeclient.js
+++ b/services/sync/modules/jpakeclient.js
@@ -281,8 +281,7 @@ JPAKEClient.prototype = {
     let rng = Cc["@mozilla.org/security/random-generator;1"]
                 .createInstance(Ci.nsIRandomGenerator);
     let bytes = rng.generateRandomBytes(JPAKE_LENGTH_CLIENTID / 2);
-    this._clientID = [("0" + byte.toString(16)).slice(-2)
-                      for each (byte in bytes)].join("");
+    this._clientID = bytes.map(byte => ("0" + byte.toString(16)).slice(-2)).join("");
   },
 
   _createSecret: function _createSecret() {
@@ -291,8 +290,7 @@ JPAKEClient.prototype = {
     let rng = Cc["@mozilla.org/security/random-generator;1"]
                 .createInstance(Ci.nsIRandomGenerator);
     let bytes = rng.generateRandomBytes(JPAKE_LENGTH_SECRET);
-    return [key[Math.floor(byte * key.length / 256)]
-            for each (byte in bytes)].join("");
+    return bytes.map(byte => key[Math.floor(byte * key.length / 256)]).join("");
   },
 
   _newRequest: function _newRequest(uri) {
diff --git a/services/sync/modules/record.js b/services/sync/modules/record.js
index 95f70cd1ad7..654a88aef0a 100644
--- a/services/sync/modules/record.js
+++ b/services/sync/modules/record.js
@@ -312,7 +312,7 @@ CollectionKeyManager.prototype = {
     // Return a sorted, unique array.
     changed.sort();
     let last;
-    changed = [x for each (x in changed) if ((x != last) && (last = x))];
+    changed = changed.filter(x => (x != last) && (last = x));
     return {same: changed.length == 0,
             changed: changed};
   },
diff --git a/services/sync/modules/service.js b/services/sync/modules/service.js
index 8ea99a2454b..5e78051cece 100644
--- a/services/sync/modules/service.js
+++ b/services/sync/modules/service.js
@@ -442,7 +442,7 @@ Sync11Service.prototype = {
 
     // Map each old pref to the current pref branch
     let oldPref = new Preferences(oldPrefBranch);
-    for each (let pref in oldPrefNames)
+    for (let pref of oldPrefNames)
       Svc.Prefs.set(pref, oldPref.get(pref));
 
     // Remove all the old prefs and remember that we've migrated
@@ -901,7 +901,7 @@ Sync11Service.prototype = {
     // Deletion doesn't make sense if we aren't set up yet!
     if (this.clusterURL != "") {
       // Clear client-specific data from the server, including disabled engines.
-      for each (let engine in [this.clientsEngine].concat(this.engineManager.getAll())) {
+      for (let engine of [this.clientsEngine].concat(this.engineManager.getAll())) {
         try {
           engine.removeClientData();
         } catch(ex) {
@@ -1511,7 +1511,7 @@ Sync11Service.prototype = {
 
     // Wipe everything we know about except meta because we just uploaded it
     let engines = [this.clientsEngine].concat(this.engineManager.getAll());
-    let collections = [engine.name for each (engine in engines)];
+    let collections = engines.map(engine => engine.name);
     // TODO: there's a bug here. We should be calling resetClient, no?
 
     // Generate, upload, and download new keys. Do this last so we don't wipe
@@ -1593,7 +1593,7 @@ Sync11Service.prototype = {
     }
 
     // Fully wipe each engine if it's able to decrypt data
-    for each (let engine in engines) {
+    for (let engine of engines) {
       if (engine.canDecrypt()) {
         engine.wipeClient();
       }
@@ -1671,7 +1671,7 @@ Sync11Service.prototype = {
       }
 
       // Have each engine drop any temporary meta data
-      for each (let engine in engines) {
+      for (let engine of engines) {
         engine.resetClient();
       }
     })();
diff --git a/services/sync/modules/stages/declined.js b/services/sync/modules/stages/declined.js
index 3c53e2c75c9..ff8a141812d 100644
--- a/services/sync/modules/stages/declined.js
+++ b/services/sync/modules/stages/declined.js
@@ -29,8 +29,8 @@ this.DeclinedEngines = function (service) {
 }
 this.DeclinedEngines.prototype = {
   updateDeclined: function (meta, engineManager=this.service.engineManager) {
-    let enabled = new Set([e.name for each (e in engineManager.getEnabled())]);
-    let known = new Set([e.name for each (e in engineManager.getAll())]);
+    let enabled = new Set(engineManager.getEnabled().map(e => e.name));
+    let known = new Set(engineManager.getAll().map(e => e.name));
     let remoteDeclined = new Set(meta.payload.declined || []);
     let localDeclined = new Set(engineManager.getDeclined());
 
diff --git a/services/sync/modules/stages/enginesync.js b/services/sync/modules/stages/enginesync.js
index f174c253d44..a2fe31b0cef 100644
--- a/services/sync/modules/stages/enginesync.js
+++ b/services/sync/modules/stages/enginesync.js
@@ -289,7 +289,7 @@ EngineSynchronizer.prototype = {
     }
 
     // Any remaining engines were either enabled locally or disabled remotely.
-    for each (let engineName in enabled) {
+    for (let engineName of enabled) {
       let engine = engineManager.get(engineName);
       if (Svc.Prefs.get("engineStatusChanged." + engine.prefName, false)) {
         this._log.trace("The " + engineName + " engine was enabled locally.");
diff --git a/services/sync/tests/unit/head_appinfo.js b/services/sync/tests/unit/head_appinfo.js
index b99d4e0cb09..3ade823f7b4 100644
--- a/services/sync/tests/unit/head_appinfo.js
+++ b/services/sync/tests/unit/head_appinfo.js
@@ -60,7 +60,7 @@ registrar.registerFactory(Components.ID("{fbfae60b-64a4-44ef-a911-08ceb70b9f31}"
 function addResourceAlias() {
   const resProt = Services.io.getProtocolHandler("resource")
                           .QueryInterface(Ci.nsIResProtocolHandler);
-  for each (let s in ["common", "sync", "crypto"]) {
+  for (let s of ["common", "sync", "crypto"]) {
     let uri = Services.io.newURI("resource://gre/modules/services-" + s + "/", null,
                                  null);
     resProt.setSubstitution("services-" + s, uri);
diff --git a/services/sync/tests/unit/head_http_server.js b/services/sync/tests/unit/head_http_server.js
index c78faf5eb91..f215e47fe91 100644
--- a/services/sync/tests/unit/head_http_server.js
+++ b/services/sync/tests/unit/head_http_server.js
@@ -309,7 +309,8 @@ ServerCollection.prototype = {
 
     // This will count records where we have an existing ServerWBO
     // registered with us as successful and all other records as failed.
-    for each (let record in input) {
+    for (let key in input) {
+      let record = input[key];
       let wbo = this.wbo(record.id);
       if (!wbo && this.acceptNew) {
         this._log.debug("Creating WBO " + JSON.stringify(record.id) +
@@ -354,7 +355,7 @@ ServerCollection.prototype = {
 
       // Parse queryString
       let options = {};
-      for each (let chunk in request.queryString.split("&")) {
+      for (let chunk of request.queryString.split("&")) {
         if (!chunk) {
           continue;
         }
@@ -704,7 +705,8 @@ SyncServer.prototype = {
       throw new Error("Unknown user.");
     }
     let userCollections = this.users[username].collections;
-    for each (let [name, coll] in Iterator(userCollections)) {
+    for (let name in userCollections) {
+      let coll = userCollections[name];
       this._log.trace("Bulk deleting " + name + " for " + username + "...");
       coll.delete({});
     }
@@ -768,7 +770,10 @@ SyncServer.prototype = {
    */
   respond: function respond(req, resp, code, status, body, headers) {
     resp.setStatusLine(req.httpVersion, code, status);
-    for each (let [header, value] in Iterator(headers || this.defaultHeaders)) {
+    if (!headers)
+      headers = this.defaultHeaders;
+    for (let header in headers) {
+      let value = headers[header];
       resp.setHeader(header, value);
     }
     resp.setHeader("X-Weave-Timestamp", "" + this.timestamp(), false);
diff --git a/services/sync/tests/unit/test_addons_reconciler.js b/services/sync/tests/unit/test_addons_reconciler.js
index 8cfa37d78f4..d93bdfc0380 100644
--- a/services/sync/tests/unit/test_addons_reconciler.js
+++ b/services/sync/tests/unit/test_addons_reconciler.js
@@ -71,7 +71,7 @@ add_test(function test_install_detection() {
 
   const KEYS = ["id", "guid", "enabled", "installed", "modified", "type",
                 "scope", "foreignInstall"];
-  for each (let key in KEYS) {
+  for (let key of KEYS) {
     do_check_true(key in record);
     do_check_neq(null, record[key]);
   }
diff --git a/services/sync/tests/unit/test_addons_store.js b/services/sync/tests/unit/test_addons_store.js
index d79c18a3f4b..6bb78787ad1 100644
--- a/services/sync/tests/unit/test_addons_store.js
+++ b/services/sync/tests/unit/test_addons_store.js
@@ -204,7 +204,7 @@ add_test(function test_addon_syncability() {
 
   let dummy = {};
   const KEYS = ["id", "syncGUID", "type", "scope", "foreignInstall"];
-  for each (let k in KEYS) {
+  for (let k of KEYS) {
     dummy[k] = addon[k];
   }
 
@@ -243,16 +243,16 @@ add_test(function test_addon_syncability() {
     "https://untrusted.example.com/foo", // non-trusted hostname`
   ];
 
-  for each (let uri in trusted) {
+  for (let uri of trusted) {
     do_check_true(store.isSourceURITrusted(createURI(uri)));
   }
 
-  for each (let uri in untrusted) {
+  for (let uri of untrusted) {
     do_check_false(store.isSourceURITrusted(createURI(uri)));
   }
 
   Svc.Prefs.set("addons.trustedSourceHostnames", "");
-  for each (let uri in trusted) {
+  for (let uri of trusted) {
     do_check_false(store.isSourceURITrusted(createURI(uri)));
   }
 
@@ -278,7 +278,7 @@ add_test(function test_ignore_hotfixes() {
 
   let dummy = {};
   const KEYS = ["id", "syncGUID", "type", "scope", "foreignInstall"];
-  for each (let k in KEYS) {
+  for (let k of KEYS) {
     dummy[k] = addon[k];
   }
 
diff --git a/services/sync/tests/unit/test_bookmark_store.js b/services/sync/tests/unit/test_bookmark_store.js
index ec6d51fba9b..ad16130852d 100644
--- a/services/sync/tests/unit/test_bookmark_store.js
+++ b/services/sync/tests/unit/test_bookmark_store.js
@@ -80,8 +80,8 @@ add_test(function test_bookmark_create() {
     _("Have the store create a new record object. Verify that it has the same data.");
     let newrecord = store.createRecord(fxrecord.id);
     do_check_true(newrecord instanceof Bookmark);
-    for each (let property in ["type", "bmkUri", "description", "title",
-                               "keyword", "parentName", "parentid"]) {
+    for (let property of ["type", "bmkUri", "description", "title",
+                          "keyword", "parentName", "parentid"]) {
       do_check_eq(newrecord[property], fxrecord[property]);
     }
     do_check_true(Utils.deepEquals(newrecord.tags.sort(),
@@ -197,7 +197,7 @@ add_test(function test_folder_create() {
     _("Have the store create a new record object. Verify that it has the same data.");
     let newrecord = store.createRecord(folder.id);
     do_check_true(newrecord instanceof BookmarkFolder);
-    for each (let property in ["title", "parentName", "parentid"])
+    for (let property of ["title", "parentName", "parentid"])
       do_check_eq(newrecord[property], folder[property]);
 
     _("Folders have high sort index to ensure they're synced first.");
diff --git a/services/sync/tests/unit/test_clients_engine.js b/services/sync/tests/unit/test_clients_engine.js
index 2898d9eb334..e571be724f1 100644
--- a/services/sync/tests/unit/test_clients_engine.js
+++ b/services/sync/tests/unit/test_clients_engine.js
@@ -328,7 +328,7 @@ add_test(function test_command_validation() {
     ["__UNKNOWN__", [],       false]
   ];
 
-  for each (let [action, args, expectedResult] in testCommands) {
+  for (let [action, args, expectedResult] of testCommands) {
     let remoteId = Utils.makeGUID();
     let rec = new ClientsRec("clients", remoteId);
 
diff --git a/services/sync/tests/unit/test_collections_recovery.js b/services/sync/tests/unit/test_collections_recovery.js
index 377a05383d6..06ec0ab8c16 100644
--- a/services/sync/tests/unit/test_collections_recovery.js
+++ b/services/sync/tests/unit/test_collections_recovery.js
@@ -33,7 +33,7 @@ add_identity_test(this, function test_missing_crypto_collection() {
   };
   let collections = ["clients", "bookmarks", "forms", "history",
                      "passwords", "prefs", "tabs"];
-  for each (let coll in collections) {
+  for (let coll of collections) {
     handlers["/1.1/johndoe/storage/" + coll] =
       johnU(coll, new ServerCollection({}, true).handler());
   }
diff --git a/services/sync/tests/unit/test_jpakeclient.js b/services/sync/tests/unit/test_jpakeclient.js
index 7de35fe2f4c..783edb46037 100644
--- a/services/sync/tests/unit/test_jpakeclient.js
+++ b/services/sync/tests/unit/test_jpakeclient.js
@@ -369,7 +369,7 @@ add_test(function test_wrongPIN() {
     displayPIN: function displayPIN(pin) {
       this.cid = pin.slice(JPAKE_LENGTH_SECRET);
       let secret = pin.slice(0, JPAKE_LENGTH_SECRET);
-      secret = [char for each (char in secret)].reverse().join("");
+      secret = Array.prototype.slice.call(secret).reverse().join("");
       let new_pin = secret + this.cid;
       _("Received PIN " + pin + ", but I'm entering " + new_pin);
 
diff --git a/services/sync/tests/unit/test_resource.js b/services/sync/tests/unit/test_resource.js
index a7be57ded3d..1dc9daec351 100644
--- a/services/sync/tests/unit/test_resource.js
+++ b/services/sync/tests/unit/test_resource.js
@@ -140,7 +140,7 @@ function server_headers(metadata, response) {
   header_names = header_names.sort();
 
   headers = {};
-  for each (let header in header_names) {
+  for (let header of header_names) {
     headers[header] = metadata.getHeader(header);
   }
   let body = JSON.stringify(headers);
diff --git a/services/sync/tests/unit/test_resource_async.js b/services/sync/tests/unit/test_resource_async.js
index 9420f211872..0db91a1b59f 100644
--- a/services/sync/tests/unit/test_resource_async.js
+++ b/services/sync/tests/unit/test_resource_async.js
@@ -140,7 +140,7 @@ function server_headers(metadata, response) {
   header_names = header_names.sort();
 
   headers = {};
-  for each (let header in header_names) {
+  for (let header of header_names) {
     headers[header] = metadata.getHeader(header);
   }
   let body = JSON.stringify(headers);
diff --git a/services/sync/tests/unit/test_service_startup.js b/services/sync/tests/unit/test_service_startup.js
index 6ced39da931..7d96cad5288 100644
--- a/services/sync/tests/unit/test_service_startup.js
+++ b/services/sync/tests/unit/test_service_startup.js
@@ -29,7 +29,7 @@ function run_test() {
 
   _("Engines are registered.");
   let engines = Service.engineManager.getAll();
-  do_check_true(Utils.deepEquals([engine.name for each (engine in engines)],
+  do_check_true(Utils.deepEquals(engines.map(engine => engine.name),
                                  ['tabs', 'bookmarks', 'forms', 'history']));
 
   _("Observers are notified of startup");
diff --git a/services/sync/tests/unit/test_status.js b/services/sync/tests/unit/test_status.js
index bc2d67f425f..378aafe9083 100644
--- a/services/sync/tests/unit/test_status.js
+++ b/services/sync/tests/unit/test_status.js
@@ -18,9 +18,9 @@ function run_test() {
 
 
   // Check login status
-  for each (let code in [LOGIN_FAILED_NO_USERNAME,
-                         LOGIN_FAILED_NO_PASSWORD,
-                         LOGIN_FAILED_NO_PASSPHRASE]) {
+  for (let code of [LOGIN_FAILED_NO_USERNAME,
+                    LOGIN_FAILED_NO_PASSWORD,
+                    LOGIN_FAILED_NO_PASSPHRASE]) {
     Status.login = code;
     do_check_eq(Status.login, code);
     do_check_eq(Status.service, CLIENT_NOT_CONFIGURED);
diff --git a/services/sync/tests/unit/test_tab_tracker.js b/services/sync/tests/unit/test_tab_tracker.js
index f0bff3cc91d..4605b066a94 100644
--- a/services/sync/tests/unit/test_tab_tracker.js
+++ b/services/sync/tests/unit/test_tab_tracker.js
@@ -53,7 +53,7 @@ function run_test() {
   logs = fakeSvcWinMediator();
   Svc.Obs.notify("weave:engine:start-tracking");
   do_check_eq(logs.length, 2);
-  for each (let log in logs) {
+  for (let log of logs) {
     do_check_eq(log.addTopics.length, 5);
     do_check_true(log.addTopics.indexOf("pageshow") >= 0);
     do_check_true(log.addTopics.indexOf("TabOpen") >= 0);
@@ -67,7 +67,7 @@ function run_test() {
   logs = fakeSvcWinMediator();
   Svc.Obs.notify("weave:engine:stop-tracking");
   do_check_eq(logs.length, 2);
-  for each (let log in logs) {
+  for (let log of logs) {
     do_check_eq(log.addTopics.length, 0);
     do_check_eq(log.remTopics.length, 5);
     do_check_true(log.remTopics.indexOf("pageshow") >= 0);
@@ -78,7 +78,7 @@ function run_test() {
   }
 
   _("Test tab listener");
-  for each (let evttype in ["TabOpen", "TabClose", "TabSelect"]) {
+  for (let evttype of ["TabOpen", "TabClose", "TabSelect"]) {
     // Pretend we just synced.
     tracker.clearChangedIDs();
     do_check_false(tracker.modified);
diff --git a/services/sync/tps/extensions/mozmill/resource/driver/controller.js b/services/sync/tps/extensions/mozmill/resource/driver/controller.js
index 846b9fc893d..6acc078e7fe 100644
--- a/services/sync/tps/extensions/mozmill/resource/driver/controller.js
+++ b/services/sync/tps/extensions/mozmill/resource/driver/controller.js
@@ -44,7 +44,11 @@ waitForEvents.prototype = {
     node.firedEvents = {};
     this.registry = {};
 
-    for each (var e in events) {
+    if (!events) {
+      return;
+    }
+    for (var key in events) {
+      var e = events[key];
       var listener = function (event) {
         this.firedEvents[event.type] = true;
       }
diff --git a/services/sync/tps/extensions/mozmill/resource/driver/elementslib.js b/services/sync/tps/extensions/mozmill/resource/driver/elementslib.js
index ea371e5e6e1..4bf35a3846d 100644
--- a/services/sync/tps/extensions/mozmill/resource/driver/elementslib.js
+++ b/services/sync/tps/extensions/mozmill/resource/driver/elementslib.js
@@ -304,7 +304,7 @@ var _returnResult = function (results) {
 
 var _forChildren = function (element, name, value) {
   var results = [];
-  var nodes = [e for each (e in element.childNodes) if (e)]
+  var nodes = Array.from(element.childNodes).filter(e => e);
 
   for (var i in nodes) {
     var n = nodes[i];
@@ -318,7 +318,7 @@ var _forChildren = function (element, name, value) {
 
 var _forAnonChildren = function (_document, element, name, value) {
   var results = [];
-  var nodes = [e for each (e in _document.getAnoymousNodes(element)) if (e)];
+  var nodes = Array.from(_document.getAnoymousNodes(element)).filter(e => e);
 
   for (var i in nodes ) {
     var n = nodes[i];
@@ -381,7 +381,7 @@ var _byAnonAttrib = function (_document, parent, attributes) {
     }
   }
 
-  var nodes = [n for each (n in _document.getAnonymousNodes(parent)) if (n.getAttribute)];
+  var nodes = Array.from(_document.getAnonymousNodes(parent)).filter(n => n.getAttribute);
 
   function resultsForNodes (nodes) {
     for (var i in nodes) {
@@ -404,7 +404,7 @@ var _byAnonAttrib = function (_document, parent, attributes) {
 
   resultsForNodes(nodes);
   if (results.length == 0) {
-    resultsForNodes([n for each (n in parent.childNodes) if (n != undefined && n.getAttribute)])
+    resultsForNodes(Array.from(parent.childNodes).filter(n => n != undefined && n.getAttribute));
   }
 
   return _returnResult(results)
@@ -440,7 +440,7 @@ function Lookup(_document, expression) {
     throw new Error('Lookup constructor did not recieve enough arguments.');
   }
 
-  var expSplit = [e for each (e in smartSplit(expression) ) if (e != '')];
+  var expSplit = smartSplit(expression).filter(e => e != '');
   expSplit.unshift(_document);
 
   var nCases = {'id':_byID, 'name':_byName, 'attrib':_byAttrib, 'index':_byIndex};
diff --git a/services/sync/tps/extensions/mozmill/resource/modules/frame.js b/services/sync/tps/extensions/mozmill/resource/modules/frame.js
index 9f0c325bec2..dae8276b620 100644
--- a/services/sync/tps/extensions/mozmill/resource/modules/frame.js
+++ b/services/sync/tps/extensions/mozmill/resource/modules/frame.js
@@ -256,7 +256,7 @@ events.pass = function (obj) {
     events.currentTest.__passes__.push(obj);
   }
 
-  for each (var timer in timers) {
+  for (var timer of timers) {
     timer.actions.push(
       {"currentTest": events.currentModule.__file__ + "::" + events.currentTest.__name__,
        "obj": obj,
@@ -286,7 +286,7 @@ events.fail = function (obj) {
     events.currentTest.__fails__.push(obj);
   }
 
-  for each (var time in timers) {
+  for (var time of timers) {
     timer.actions.push(
       {"currentTest": events.currentModule.__file__ + "::" + events.currentTest.__name__,
        "obj": obj,
@@ -325,7 +325,7 @@ events.fireEvent = function (name, obj) {
     }
   }
 
-  for each(var listener in this.globalListeners) {
+  for (var listener of this.globalListeners) {
     listener(name, obj);
   }
 }
diff --git a/services/sync/tps/extensions/mozmill/resource/stdlib/os.js b/services/sync/tps/extensions/mozmill/resource/stdlib/os.js
index 58fa5a41cf8..ce88bea8a8c 100644
--- a/services/sync/tps/extensions/mozmill/resource/stdlib/os.js
+++ b/services/sync/tps/extensions/mozmill/resource/stdlib/os.js
@@ -37,7 +37,7 @@ function abspath(rel, file) {
     file = file.parent;
   }
 
-  for each(var p in relSplit) {
+  for (var p of relSplit) {
     if (p == '..') {
       file = file.parent;
     } else if (p == '.') {
diff --git a/services/sync/tps/extensions/mozmill/resource/stdlib/securable-module.js b/services/sync/tps/extensions/mozmill/resource/stdlib/securable-module.js
index 794c3e2c24c..bfa7ef5a9fe 100644
--- a/services/sync/tps/extensions/mozmill/resource/stdlib/securable-module.js
+++ b/services/sync/tps/extensions/mozmill/resource/stdlib/securable-module.js
@@ -168,8 +168,7 @@
        if (rootPaths) {
          if (rootPaths.constructor.name != "Array")
            rootPaths = [rootPaths];
-         var fses = [new exports.LocalFileSystem(path)
-                     for each (path in rootPaths)];
+         var fses = rootPaths.map(path => new exports.LocalFileSystem(path));
          options.fs = new exports.CompositeFileSystem(fses);
        } else
          options.fs = new exports.LocalFileSystem();
diff --git a/services/sync/tps/extensions/mozmill/resource/stdlib/utils.js b/services/sync/tps/extensions/mozmill/resource/stdlib/utils.js
index 659d6111bbc..73e13e11f16 100644
--- a/services/sync/tps/extensions/mozmill/resource/stdlib/utils.js
+++ b/services/sync/tps/extensions/mozmill/resource/stdlib/utils.js
@@ -83,7 +83,7 @@ function getWindows(type) {
 }
 
 function getMethodInWindows(methodName) {
-  for each (var w in getWindows()) {
+  for (var w of getWindows()) {
     if (w[methodName] != undefined) {
       return w[methodName];
     }
@@ -93,7 +93,7 @@ function getMethodInWindows(methodName) {
 }
 
 function getWindowByTitle(title) {
-  for each (var w in getWindows()) {
+  for (var w of getWindows()) {
     if (w.document.title && w.document.title == title) {
       return w;
     }
diff --git a/services/sync/tps/extensions/tps/resource/modules/history.jsm b/services/sync/tps/extensions/tps/resource/modules/history.jsm
index aa2c2f36155..20edfc9a6f7 100644
--- a/services/sync/tps/extensions/tps/resource/modules/history.jsm
+++ b/services/sync/tps/extensions/tps/resource/modules/history.jsm
@@ -33,7 +33,7 @@ var DumpHistory = function TPS_History__DumpHistory() {
     let node = root.getChild(i);
     let uri = node.uri;
     let curvisits = HistoryEntry._getVisits(uri);
-    for each (var visit in curvisits) {
+    for (var visit of curvisits) {
       Logger.logInfo("URI: " + uri + ", type=" + visit.type + ", date=" + visit.date, true);
     }
   }
@@ -110,7 +110,7 @@ var HistoryEntry = {
       uri: uri,
       visits: []
     };
-    for each (visit in item.visits) {
+    for (let visit of item.visits) {
       place.visits.push({
         visitDate: usSinceEpoch + (visit.date * 60 * 60 * 1000 * 1000),
         transitionType: visit.type
@@ -150,8 +150,8 @@ var HistoryEntry = {
       "History entry in test file must have both 'visits' " +
       "and 'uri' properties");
     let curvisits = this._getVisits(item.uri);
-    for each (visit in curvisits) {
-      for each (itemvisit in item.visits) {
+    for (let visit of curvisits) {
+      for (let itemvisit of item.visits) {
         let expectedDate = itemvisit.date * 60 * 60 * 1000 * 1000
             + usSinceEpoch;
         if (visit.type == itemvisit.type && visit.date == expectedDate) {
@@ -161,7 +161,7 @@ var HistoryEntry = {
     }
 
     let all_items_found = true;
-    for each (itemvisit in item.visits) {
+    for (let itemvisit in item.visits) {
       all_items_found = all_items_found && "found" in itemvisit;
       Logger.logInfo("History entry for " + item.uri + ", type:" +
               itemvisit.type + ", date:" + itemvisit.date +
diff --git a/services/sync/tps/extensions/tps/resource/modules/tabs.jsm b/services/sync/tps/extensions/tps/resource/modules/tabs.jsm
index c454ef9f442..f6caf06c6cd 100644
--- a/services/sync/tps/extensions/tps/resource/modules/tabs.jsm
+++ b/services/sync/tps/extensions/tps/resource/modules/tabs.jsm
@@ -50,7 +50,11 @@ var BrowserTabs = {
     // Find the uri in Weave's list of tabs for the given profile.
     let engine = Weave.Service.engineManager.get("tabs");
     for (let [guid, client] in Iterator(engine.getAllClients())) {
-      for each (tab in client.tabs) {
+      if (!client.tabs) {
+        continue;
+      }
+      for (let key in client.tabs) {
+        let tab = client.tabs[key];
         let weaveTabUrl = tab.urlHistory[0];
         if (uri == weaveTabUrl && profile == client.clientName)
           if (title == undefined || title == tab.title)
diff --git a/services/sync/tps/extensions/tps/resource/tps.jsm b/services/sync/tps/extensions/tps/resource/tps.jsm
index 1a2439ab27d..422ba314551 100644
--- a/services/sync/tps/extensions/tps/resource/tps.jsm
+++ b/services/sync/tps/extensions/tps/resource/tps.jsm
@@ -285,7 +285,7 @@ var TPS = {
   HandleTabs: function (tabs, action) {
     this._tabsAdded = tabs.length;
     this._tabsFinished = 0;
-    for each (let tab in tabs) {
+    for (let tab of tabs) {
       Logger.logInfo("executing action " + action.toUpperCase() +
                      " on tab " + JSON.stringify(tab));
       switch(action) {
@@ -330,7 +330,7 @@ var TPS = {
   },
 
   HandlePrefs: function (prefs, action) {
-    for each (pref in prefs) {
+    for (let pref of prefs) {
       Logger.logInfo("executing action " + action.toUpperCase() +
                      " on pref " + JSON.stringify(pref));
       let preference = new Preference(pref);
@@ -349,7 +349,7 @@ var TPS = {
   },
 
   HandleForms: function (data, action) {
-    for each (datum in data) {
+    for (let datum of data) {
       Logger.logInfo("executing action " + action.toUpperCase() +
                      " on form entry " + JSON.stringify(datum));
       let formdata = new FormData(datum, this._usSinceEpoch);
@@ -377,7 +377,7 @@ var TPS = {
 
   HandleHistory: function (entries, action) {
     try {
-      for each (entry in entries) {
+      for (let entry of entries) {
         Logger.logInfo("executing action " + action.toUpperCase() +
                        " on history entry " + JSON.stringify(entry));
         switch(action) {
@@ -410,7 +410,7 @@ var TPS = {
 
   HandlePasswords: function (passwords, action) {
     try {
-      for each (password in passwords) {
+      for (let password of passwords) {
         let password_id = -1;
         Logger.logInfo("executing action " + action.toUpperCase() +
                       " on password " + JSON.stringify(password));
@@ -450,7 +450,7 @@ var TPS = {
   },
 
   HandleAddons: function (addons, action, state) {
-    for each (let entry in addons) {
+    for (let entry of addons) {
       Logger.logInfo("executing action " + action.toUpperCase() +
                      " on addon " + JSON.stringify(entry));
       let addon = new Addon(this, entry);
@@ -481,9 +481,9 @@ var TPS = {
   HandleBookmarks: function (bookmarks, action) {
     try {
       let items = [];
-      for (folder in bookmarks) {
+      for (let folder in bookmarks) {
         let last_item_pos = -1;
-        for each (bookmark in bookmarks[folder]) {
+        for (let bookmark of bookmarks[folder]) {
           Logger.clearPotentialError();
           let placesItem;
           bookmark['location'] = folder;
@@ -525,7 +525,7 @@ var TPS = {
       }
 
       if (action == ACTION_DELETE || action == ACTION_MODIFY) {
-        for each (item in items) {
+        for (let item of items) {
           Logger.logInfo("executing action " + action.toUpperCase() +
                          " on bookmark " + JSON.stringify(item));
           switch(action) {
@@ -689,7 +689,7 @@ var TPS = {
       // care about.
       if (settings.ignoreUnusedEngines && Array.isArray(this._enabledEngines)) {
         let names = {};
-        for each (let name in this._enabledEngines) {
+        for (let name of this._enabledEngines) {
           names[name] = true;
         }