diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-change-actions-js-api.js b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-change-actions-js-api.js
index 9bcde07cb4..99c4fed01c 100644
--- a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-change-actions-js-api.js
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-change-actions-js-api.js
@@ -22,13 +22,13 @@
   }
 
   GrChangeActionsInterface.prototype.addPrimaryActionKey = function(key) {
-    if (this._el.primaryActionKeys.indexOf(key) !== -1) { return; }
+    if (this._el.primaryActionKeys.includes(key)) { return; }
 
     this._el.push('primaryActionKeys', key);
   };
 
   GrChangeActionsInterface.prototype.removePrimaryActionKey = function(key) {
-    this._el.primaryActionKeys = this._el.primaryActionKeys.filter(function(k) {
+    this._el.primaryActionKeys = this._el.primaryActionKeys.filter(k => {
       return k !== key;
     });
   };
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-change-actions-js-api_test.html b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-change-actions-js-api_test.html
index d964cdec60..24fee3944e 100644
--- a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-change-actions-js-api_test.html
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-change-actions-js-api_test.html
@@ -37,43 +37,44 @@ breaking changes to gr-change-actions won’t be noticed.
 </test-fixture>
 
 <script>
-  suite('gr-js-api-interface tests', function() {
-    var element;
-    var changeActions;
+  suite('gr-js-api-interface tests', () => {
+    let element;
+    let changeActions;
 
     // Because deepEqual doesn’t behave in Safari.
     function assertArraysEqual(actual, expected) {
       assert.equal(actual.length, expected.length);
-      for (var i = 0; i < actual.length; i++) {
+      for (let i = 0; i < actual.length; i++) {
         assert.equal(actual[i], expected[i]);
       }
     }
 
-    setup(function() {
+    setup(() => {
       element = fixture('basic');
       element.change = {};
       element._hasKnownChainState = false;
-      var plugin;
-      Gerrit.install(function(p) { plugin = p; }, '0.1',
+      let plugin;
+      Gerrit.install(p => { plugin = p; }, '0.1',
           'http://test.com/plugins/testplugin/static/test.js');
       changeActions = plugin.changeActions();
     });
 
-    teardown(function() {
+    teardown(() => {
       changeActions = null;
     });
 
-    test('property existence', function() {
-      [
+    test('property existence', () => {
+      const properties = [
         'ActionType',
         'ChangeActions',
         'RevisionActions',
-      ].forEach(function(p) {
+      ];
+      for (const p of properties) {
         assertArraysEqual(changeActions[p], element[p]);
-      });
+      }
     });
 
-    test('add/remove primary action keys', function() {
+    test('add/remove primary action keys', () => {
       element.primaryActionKeys = [];
       changeActions.addPrimaryActionKey('foo');
       assertArraysEqual(element.primaryActionKeys, ['foo']);
@@ -89,34 +90,34 @@ breaking changes to gr-change-actions won’t be noticed.
       assertArraysEqual(element.primaryActionKeys, []);
     });
 
-    test('action buttons', function(done) {
-      var key = changeActions.add(changeActions.ActionType.REVISION, 'Bork!');
-      var handler = sinon.spy();
+    test('action buttons', done => {
+      const key = changeActions.add(changeActions.ActionType.REVISION, 'Bork!');
+      const handler = sinon.spy();
       changeActions.addTapListener(key, handler);
-      flush(function() {
+      flush(() => {
         MockInteractions.tap(element.$$('[data-action-key="' + key + '"]'));
         assert(handler.calledOnce);
         changeActions.removeTapListener(key, handler);
         MockInteractions.tap(element.$$('[data-action-key="' + key + '"]'));
         assert(handler.calledOnce);
         changeActions.remove(key);
-        flush(function() {
+        flush(() => {
           assert.isNull(element.$$('[data-action-key="' + key + '"]'));
           done();
         });
       });
     });
 
-    test('action button properties', function(done) {
-      var key = changeActions.add(changeActions.ActionType.REVISION, 'Bork!');
-      flush(function() {
-        var button = element.$$('[data-action-key="' + key + '"]');
+    test('action button properties', done => {
+      const key = changeActions.add(changeActions.ActionType.REVISION, 'Bork!');
+      flush(() => {
+        const button = element.$$('[data-action-key="' + key + '"]');
         assert.isOk(button);
         assert.equal(button.getAttribute('data-label'), 'Bork!');
         assert.isNotOk(button.disabled);
         changeActions.setLabel(key, 'Yo');
         changeActions.setEnabled(key, false);
-        flush(function() {
+        flush(() => {
           assert.equal(button.getAttribute('data-label'), 'Yo');
           assert.isTrue(button.disabled);
           done();
@@ -124,30 +125,30 @@ breaking changes to gr-change-actions won’t be noticed.
       });
     });
 
-    test('hide action buttons', function(done) {
-      var key = changeActions.add(changeActions.ActionType.REVISION, 'Bork!');
-      flush(function() {
-        var button = element.$$('[data-action-key="' + key + '"]');
+    test('hide action buttons', done => {
+      const key = changeActions.add(changeActions.ActionType.REVISION, 'Bork!');
+      flush(() => {
+        const button = element.$$('[data-action-key="' + key + '"]');
         assert.isOk(button);
         assert.isFalse(button.hasAttribute('hidden'));
         changeActions.setActionHidden(
             changeActions.ActionType.REVISION, key, true);
-        flush(function() {
-          var button = element.$$('[data-action-key="' + key + '"]');
+        flush(() => {
+          const button = element.$$('[data-action-key="' + key + '"]');
           assert.isNotOk(button);
           done();
         });
       });
     });
 
-    test('move action button to overflow', function(done) {
-      var key = changeActions.add(changeActions.ActionType.REVISION, 'Bork!');
-      flush(function() {
+    test('move action button to overflow', done => {
+      const key = changeActions.add(changeActions.ActionType.REVISION, 'Bork!');
+      flush(() => {
         assert.isTrue(element.$.moreActions.hidden);
         assert.isOk(element.$$('[data-action-key="' + key + '"]'));
         changeActions.setActionOverflow(
             changeActions.ActionType.REVISION, key, true);
-        flush(function() {
+        flush(() => {
           assert.isNotOk(element.$$('[data-action-key="' + key + '"]'));
           assert.isFalse(element.$.moreActions.hidden);
           assert.strictEqual(element.$.moreActions.items[0].name, 'Bork!');
@@ -156,17 +157,19 @@ breaking changes to gr-change-actions won’t be noticed.
       });
     });
 
-    test('change actions priority', function(done) {
-      var key1 = changeActions.add(changeActions.ActionType.REVISION, 'Bork!');
-      var key2 = changeActions.add(changeActions.ActionType.CHANGE, 'Squanch?');
-      flush(function() {
-        var buttons =
+    test('change actions priority', done => {
+      const key1 =
+          changeActions.add(changeActions.ActionType.REVISION, 'Bork!');
+      const key2 =
+          changeActions.add(changeActions.ActionType.CHANGE, 'Squanch?');
+      flush(() => {
+        let buttons =
             Polymer.dom(element.root).querySelectorAll('[data-action-key]');
         assert.equal(buttons[0].getAttribute('data-action-key'), key1);
         assert.equal(buttons[1].getAttribute('data-action-key'), key2);
         changeActions.setActionPriority(
             changeActions.ActionType.REVISION, key1, 10);
-        flush(function() {
+        flush(() => {
           buttons =
               Polymer.dom(element.root).querySelectorAll('[data-action-key]');
           assert.equal(buttons[0].getAttribute('data-action-key'), key2);
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-change-reply-js-api_test.html b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-change-reply-js-api_test.html
index c2357cc4be..73f3479faa 100644
--- a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-change-reply-js-api_test.html
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-change-reply-js-api_test.html
@@ -37,35 +37,35 @@ limitations under the License.
 </test-fixture>
 
 <script>
-  suite('gr-change-reply-js-api tests', function() {
-    var element;
-    var sandbox;
-    var changeReply;
+  suite('gr-change-reply-js-api tests', () => {
+    let element;
+    let sandbox;
+    let changeReply;
 
-    setup(function() {
+    setup(() => {
       stub('gr-rest-api-interface', {
-        getConfig: function() { return Promise.resolve({}); },
-        getAccount: function() { return Promise.resolve(null); },
+        getConfig() { return Promise.resolve({}); },
+        getAccount() { return Promise.resolve(null); },
       });
       element = fixture('basic');
       sandbox = sinon.sandbox.create();
-      var plugin;
-      Gerrit.install(function(p) { plugin = p; }, '0.1',
+      let plugin;
+      Gerrit.install(p => { plugin = p; }, '0.1',
           'http://test.com/plugins/testplugin/static/test.js');
       changeReply = plugin.changeReply();
     });
 
-    teardown(function() {
+    teardown(() => {
       changeReply = null;
       sandbox.restore();
     });
 
-    test('calls', function() {
-      var setLabelValueStub = sinon.stub(element, 'setLabelValue');
+    test('calls', () => {
+      const setLabelValueStub = sinon.stub(element, 'setLabelValue');
       changeReply.setLabelValue('My-Label', '+1337');
       assert(setLabelValueStub.calledWithExactly('My-Label', '+1337'));
 
-      var sendStub = sinon.stub(element, 'send');
+      const sendStub = sinon.stub(element, 'send');
       changeReply.send(false);
       assert(sendStub.calledWithExactly(false));
     });
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface.js b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface.js
index 34ca72885c..70a9bf5a3c 100644
--- a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface.js
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface.js
@@ -14,7 +14,7 @@
 (function() {
   'use strict';
 
-  var EventType = {
+  const EventType = {
     HISTORY: 'history',
     LABEL_CHANGE: 'labelchange',
     SHOW_CHANGE: 'showchange',
@@ -25,7 +25,7 @@
     POST_REVERT: 'postrevert',
   };
 
-  var Element = {
+  const Element = {
     CHANGE_ACTIONS: 'changeactions',
     REPLY_DIALOG: 'replydialog',
   };
@@ -44,11 +44,11 @@
       },
     },
 
-    Element: Element,
-    EventType: EventType,
+    Element,
+    EventType,
 
-    handleEvent: function(type, detail) {
-      Gerrit.awaitPluginsLoaded().then(function() {
+    handleEvent(type, detail) {
+      Gerrit.awaitPluginsLoaded().then(() => {
         switch (type) {
           case EventType.HISTORY:
             this._handleHistory(detail);
@@ -67,27 +67,27 @@
                 type);
             break;
         }
-      }.bind(this));
+      });
     },
 
-    addElement: function(key, el) {
+    addElement(key, el) {
       this._elements[key] = el;
     },
 
-    getElement: function(key) {
+    getElement(key) {
       return this._elements[key];
     },
 
-    addEventCallback: function(eventName, callback) {
+    addEventCallback(eventName, callback) {
       if (!this._eventCallbacks[eventName]) {
         this._eventCallbacks[eventName] = [];
       }
       this._eventCallbacks[eventName].push(callback);
     },
 
-    canSubmitChange: function(change, revision) {
-      var submitCallbacks = this._getEventCallbacks(EventType.SUBMIT_CHANGE);
-      var cancelSubmit = submitCallbacks.some(function(callback) {
+    canSubmitChange(change, revision) {
+      const submitCallbacks = this._getEventCallbacks(EventType.SUBMIT_CHANGE);
+      const cancelSubmit = submitCallbacks.some(callback => {
         try {
           return callback(change, revision) === false;
         } catch (err) {
@@ -99,28 +99,29 @@
       return !cancelSubmit;
     },
 
-    _removeEventCallbacks: function() {
-      for (var k in EventType) {
+    _removeEventCallbacks() {
+      for (const k in EventType) {
+        if (!EventType.hasOwnProperty(k)) { continue; }
         this._eventCallbacks[EventType[k]] = [];
       }
     },
 
-    _handleHistory: function(detail) {
-      this._getEventCallbacks(EventType.HISTORY).forEach(function(cb) {
+    _handleHistory(detail) {
+      for (const cb of this._getEventCallbacks(EventType.HISTORY)) {
         try {
           cb(detail.path);
         } catch (err) {
           console.error(err);
         }
-      });
+      }
     },
 
-    _handleShowChange: function(detail) {
-      this._getEventCallbacks(EventType.SHOW_CHANGE).forEach(function(cb) {
-        var change = detail.change;
-        var patchNum = detail.patchNum;
-        var revision;
-        for (var rev in change.revisions) {
+    _handleShowChange(detail) {
+      for (const cb of this._getEventCallbacks(EventType.SHOW_CHANGE)) {
+        const change = detail.change;
+        const patchNum = detail.patchNum;
+        let revision;
+        for (const rev in change.revisions) {
           if (change.revisions[rev]._number == patchNum) {
             revision = change.revisions[rev];
             break;
@@ -131,67 +132,63 @@
         } catch (err) {
           console.error(err);
         }
-      });
+      }
     },
 
-    handleCommitMessage: function(change, msg) {
-      this._getEventCallbacks(EventType.COMMIT_MSG_EDIT).forEach(
-          function(cb) {
-            try {
-              cb(change, msg);
-            } catch (err) {
-              console.error(err);
-            }
-          }
-      );
+    handleCommitMessage(change, msg) {
+      for (const cb of this._getEventCallbacks(EventType.COMMIT_MSG_EDIT)) {
+        try {
+          cb(change, msg);
+        } catch (err) {
+          console.error(err);
+        }
+      }
     },
 
-    _handleComment: function(detail) {
-      this._getEventCallbacks(EventType.COMMENT).forEach(function(cb) {
+    _handleComment(detail) {
+      for (const cb of this._getEventCallbacks(EventType.COMMENT)) {
         try {
           cb(detail.node);
         } catch (err) {
           console.error(err);
         }
-      });
+      }
     },
 
-    _handleLabelChange: function(detail) {
-      this._getEventCallbacks(EventType.LABEL_CHANGE).forEach(function(cb) {
+    _handleLabelChange(detail) {
+      for (const cb of this._getEventCallbacks(EventType.LABEL_CHANGE)) {
         try {
           cb(detail.change);
         } catch (err) {
           console.error(err);
         }
-      });
+      }
     },
 
-    modifyRevertMsg: function(change, revertMsg, origMsg) {
-      this._getEventCallbacks(EventType.REVERT).forEach(function(callback) {
+    modifyRevertMsg(change, revertMsg, origMsg) {
+      for (const cb of this._getEventCallbacks(EventType.REVERT)) {
         try {
-          revertMsg = callback(change, revertMsg, origMsg);
+          revertMsg = cb(change, revertMsg, origMsg);
         } catch (err) {
           console.error(err);
         }
-      });
+      }
       return revertMsg;
     },
 
-    getLabelValuesPostRevert: function(change) {
-      var labels = {};
-      this._getEventCallbacks(EventType.POST_REVERT).forEach(
-          function(callback) {
-            try {
-              labels = callback(change);
-            } catch (err) {
-              console.error(err);
-            }
-          }
-      );
+    getLabelValuesPostRevert(change) {
+      let labels = {};
+      for (const cb of this._getEventCallbacks(EventType.POST_REVERT)) {
+        try {
+          labels = cb(change);
+        } catch (err) {
+          console.error(err);
+        }
+      }
       return labels;
     },
 
-    _getEventCallbacks: function(type) {
+    _getEventCallbacks(type) {
       return this._eventCallbacks[type] || [];
     },
   });
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface_test.html b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface_test.html
index d62bdd81c4..c3013bdbe1 100644
--- a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface_test.html
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-js-api-interface_test.html
@@ -31,45 +31,45 @@ limitations under the License.
 </test-fixture>
 
 <script>
-  suite('gr-js-api-interface tests', function() {
-    var element;
-    var plugin;
-    var errorStub;
-    var sandbox;
+  suite('gr-js-api-interface tests', () => {
+    let element;
+    let plugin;
+    let errorStub;
+    let sandbox;
 
-    var throwErrFn = function() {
+    const throwErrFn = function() {
       throw Error('Unfortunately, this handler has stopped');
     };
 
-    setup(function() {
+    setup(() => {
       sandbox = sinon.sandbox.create();
       stub('gr-rest-api-interface', {
-        getAccount: function() {
+        getAccount() {
           return Promise.resolve({name: 'Judy Hopps'});
         },
       });
       element = fixture('basic');
       errorStub = sandbox.stub(console, 'error');
       Gerrit._setPluginsCount(1);
-      Gerrit.install(function(p) { plugin = p; }, '0.1',
+      Gerrit.install(p => { plugin = p; }, '0.1',
           'http://test.com/plugins/testplugin/static/test.js');
     });
 
-    teardown(function() {
+    teardown(() => {
       sandbox.restore();
       element._removeEventCallbacks();
       plugin = null;
     });
 
-    test('url', function() {
+    test('url', () => {
       assert.equal(plugin.url(), 'http://test.com/plugins/testplugin/');
       assert.equal(plugin.url('/static/test.js'),
           'http://test.com/plugins/testplugin/static/test.js');
     });
 
-    test('history event', function(done) {
+    test('history event', done => {
       plugin.on(element.EventType.HISTORY, throwErrFn);
-      plugin.on(element.EventType.HISTORY, function(path) {
+      plugin.on(element.EventType.HISTORY, path => {
         assert.equal(path, '/path/to/awesomesauce');
         assert.isTrue(errorStub.calledOnce);
         done();
@@ -78,13 +78,13 @@ limitations under the License.
           {path: '/path/to/awesomesauce'});
     });
 
-    test('showchange event', function(done) {
-      var testChange = {
+    test('showchange event', done => {
+      const testChange = {
         _number: 42,
         revisions: {def: {_number: 2}, abc: {_number: 1}},
       };
       plugin.on(element.EventType.SHOW_CHANGE, throwErrFn);
-      plugin.on(element.EventType.SHOW_CHANGE, function(change, revision) {
+      plugin.on(element.EventType.SHOW_CHANGE, (change, revision) => {
         assert.deepEqual(change, testChange);
         assert.deepEqual(revision, testChange.revisions.abc);
         assert.isTrue(errorStub.calledOnce);
@@ -94,28 +94,28 @@ limitations under the License.
           {change: testChange, patchNum: 1});
     });
 
-    test('handleEvent awaits plugins load', function(done) {
-      var testChange = {
+    test('handleEvent awaits plugins load', done => {
+      const testChange = {
         _number: 42,
         revisions: {def: {_number: 2}, abc: {_number: 1}},
       };
-      var spy = sandbox.spy();
+      const spy = sandbox.spy();
       Gerrit._setPluginsCount(1);
       plugin.on(element.EventType.SHOW_CHANGE, spy);
       element.handleEvent(element.EventType.SHOW_CHANGE,
           {change: testChange, patchNum: 1});
       assert.isFalse(spy.called);
       Gerrit._setPluginsCount(0);
-      flush(function() {
+      flush(() => {
         assert.isTrue(spy.called);
         done();
       });
     });
 
-    test('comment event', function(done) {
-      var testCommentNode = {foo: 'bar'};
+    test('comment event', done => {
+      const testCommentNode = {foo: 'bar'};
       plugin.on(element.EventType.COMMENT, throwErrFn);
-      plugin.on(element.EventType.COMMENT, function(commentNode) {
+      plugin.on(element.EventType.COMMENT, commentNode => {
         assert.deepEqual(commentNode, testCommentNode);
         assert.isTrue(errorStub.calledOnce);
         done();
@@ -123,7 +123,7 @@ limitations under the License.
       element.handleEvent(element.EventType.COMMENT, {node: testCommentNode});
     });
 
-    test('revert event', function() {
+    test('revert event', () => {
       function appendToRevertMsg(c, revertMsg, originalMsg) {
         return revertMsg + '\n' + originalMsg.replace(/^/gm, '> ') + '\ninfo';
       }
@@ -134,16 +134,16 @@ limitations under the License.
       plugin.on(element.EventType.REVERT, throwErrFn);
       plugin.on(element.EventType.REVERT, appendToRevertMsg);
       assert.equal(element.modifyRevertMsg(null, 'test', 'origTest'),
-                   'test\n> origTest\ninfo');
+          'test\n> origTest\ninfo');
       assert.isTrue(errorStub.calledOnce);
 
       plugin.on(element.EventType.REVERT, appendToRevertMsg);
       assert.equal(element.modifyRevertMsg(null, 'test', 'origTest'),
-                   'test\n> origTest\ninfo\n> origTest\ninfo');
+          'test\n> origTest\ninfo\n> origTest\ninfo');
       assert.isTrue(errorStub.calledTwice);
     });
 
-    test('postrevert event', function() {
+    test('postrevert event', () => {
       function getLabels(c) {
         return {'Code-Review': 1};
       }
@@ -158,10 +158,10 @@ limitations under the License.
       assert.isTrue(errorStub.calledOnce);
     });
 
-    test('commitmsgedit event', function(done) {
-      var testMsg = 'Test CL commit message';
+    test('commitmsgedit event', done => {
+      const testMsg = 'Test CL commit message';
       plugin.on(element.EventType.COMMIT_MSG_EDIT, throwErrFn);
-      plugin.on(element.EventType.COMMIT_MSG_EDIT, function(change, msg) {
+      plugin.on(element.EventType.COMMIT_MSG_EDIT, (change, msg) => {
         assert.deepEqual(msg, testMsg);
         assert.isTrue(errorStub.calledOnce);
         done();
@@ -169,10 +169,10 @@ limitations under the License.
       element.handleCommitMessage(null, testMsg);
     });
 
-    test('labelchange event', function(done) {
-      var testChange = {_number: 42};
+    test('labelchange event', done => {
+      const testChange = {_number: 42};
       plugin.on(element.EventType.LABEL_CHANGE, throwErrFn);
-      plugin.on(element.EventType.LABEL_CHANGE, function(change) {
+      plugin.on(element.EventType.LABEL_CHANGE, change => {
         assert.deepEqual(change, testChange);
         assert.isTrue(errorStub.calledOnce);
         done();
@@ -180,41 +180,41 @@ limitations under the License.
       element.handleEvent(element.EventType.LABEL_CHANGE, {change: testChange});
     });
 
-    test('submitchange', function() {
+    test('submitchange', () => {
       plugin.on(element.EventType.SUBMIT_CHANGE, throwErrFn);
-      plugin.on(element.EventType.SUBMIT_CHANGE, function() { return true; });
+      plugin.on(element.EventType.SUBMIT_CHANGE, () => { return true; });
       assert.isTrue(element.canSubmitChange());
       assert.isTrue(errorStub.calledOnce);
-      plugin.on(element.EventType.SUBMIT_CHANGE, function() { return false; });
-      plugin.on(element.EventType.SUBMIT_CHANGE, function() { return true; });
+      plugin.on(element.EventType.SUBMIT_CHANGE, () => { return false; });
+      plugin.on(element.EventType.SUBMIT_CHANGE, () => { return true; });
       assert.isFalse(element.canSubmitChange());
       assert.isTrue(errorStub.calledTwice);
     });
 
-    test('versioning', function() {
-      var callback = sandbox.spy();
+    test('versioning', () => {
+      const callback = sandbox.spy();
       Gerrit.install(callback, '0.0pre-alpha');
       assert(callback.notCalled);
     });
 
-    test('getAccount', function(done) {
-      Gerrit.getLoggedIn().then(function(loggedIn) {
+    test('getAccount', done => {
+      Gerrit.getLoggedIn().then(loggedIn => {
         assert.isTrue(loggedIn);
         done();
       });
     });
 
-    test('_setPluginsCount', function(done) {
+    test('_setPluginsCount', done => {
       stub('gr-reporting', {
-        pluginsLoaded: function() {
+        pluginsLoaded() {
           assert.equal(Gerrit._pluginsPending, 0);
           done();
-        }
+        },
       });
       Gerrit._setPluginsCount(0);
     });
 
-    test('_arePluginsLoaded', function() {
+    test('_arePluginsLoaded', () => {
       assert.isTrue(Gerrit._arePluginsLoaded());
       Gerrit._setPluginsCount(1);
       assert.isFalse(Gerrit._arePluginsLoaded());
@@ -222,12 +222,12 @@ limitations under the License.
       assert.isTrue(Gerrit._arePluginsLoaded());
     });
 
-    test('_pluginInstalled', function(done) {
+    test('_pluginInstalled', done => {
       stub('gr-reporting', {
-        pluginsLoaded: function() {
+        pluginsLoaded() {
           assert.equal(Gerrit._pluginsPending, 0);
           done();
-        }
+        },
       });
       Gerrit._setPluginsCount(2);
       Gerrit._pluginInstalled();
@@ -235,34 +235,34 @@ limitations under the License.
       Gerrit._pluginInstalled();
     });
 
-    test('install calls _pluginInstalled', function() {
+    test('install calls _pluginInstalled', () => {
       sandbox.stub(Gerrit, '_pluginInstalled');
-      Gerrit.install(function(p) { plugin = p; }, '0.1',
+      Gerrit.install(p => { plugin = p; }, '0.1',
           'http://test.com/plugins/testplugin/static/test.js');
       assert.isTrue(Gerrit._pluginInstalled.calledOnce);
     });
 
-    test('install calls _pluginInstalled on error', function() {
+    test('install calls _pluginInstalled on error', () => {
       sandbox.stub(Gerrit, '_pluginInstalled');
-      Gerrit.install(function() {}, '0.0pre-alpha');
+      Gerrit.install(() => {}, '0.0pre-alpha');
       assert.isTrue(Gerrit._pluginInstalled.calledOnce);
     });
 
-    test('installGwt calls _pluginInstalled', function() {
+    test('installGwt calls _pluginInstalled', () => {
       sandbox.stub(Gerrit, '_pluginInstalled');
       Gerrit.installGwt();
       assert.isTrue(Gerrit._pluginInstalled.calledOnce);
     });
 
-    test('installGwt returns a stub object', function() {
-      var plugin = Gerrit.installGwt();
+    test('installGwt returns a stub object', () => {
+      const plugin = Gerrit.installGwt();
       sandbox.stub(console, 'warn');
       assert.isAbove(Object.keys(plugin).length, 0);
-      Object.keys(plugin).forEach(function(name) {
+      for (const name of Object.keys(plugin)) {
         console.warn.reset();
         plugin[name]();
         assert.isTrue(console.warn.calledOnce);
-      });
+      }
     });
   });
 </script>
diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-public-js-api.js b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-public-js-api.js
index 402b371149..a84eeddd3d 100644
--- a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-public-js-api.js
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-public-js-api.js
@@ -14,17 +14,17 @@
 (function(window) {
   'use strict';
 
-  var warnNotSupported = function(opt_name) {
+  const warnNotSupported = function(opt_name) {
     console.warn('Plugin API method ' + (opt_name || '') + ' is not supported');
   };
 
-  var stubbedMethods = ['_loadedGwt', 'screen', 'settingsScreen', 'panel'];
-  var GWT_PLUGIN_STUB = {};
-  stubbedMethods.forEach(function(name) {
+  const stubbedMethods = ['_loadedGwt', 'screen', 'settingsScreen', 'panel'];
+  const GWT_PLUGIN_STUB = {};
+  for (const name of stubbedMethods) {
     GWT_PLUGIN_STUB[name] = warnNotSupported.bind(null, name);
-  });
+  }
 
-  var API_VERSION = '0.1';
+  const API_VERSION = '0.1';
 
   // GWT JSNI uses $wnd to refer to window.
   // http://www.gwtproject.org/doc/latest/DevGuideCodingBasicsJSNI.html
@@ -38,7 +38,7 @@
     }
 
     this._url = new URL(opt_url);
-    if (this._url.pathname.indexOf('/plugins') !== 0) {
+    if (!this._url.pathname.startsWith('/plugins')) {
       console.warn('Plugin not being loaded from /plugins base path:',
           this._url.href, '— Unable to determine name.');
       return;
@@ -54,14 +54,14 @@
     return this._name;
   };
 
-  Plugin.prototype.registerStyleModule =
-      function(stylingEndpointName, moduleName) {
+  Plugin.prototype.registerStyleModule = function(stylingEndpointName,
+      moduleName) {
     if (!Gerrit._styleModules[stylingEndpointName]) {
       Gerrit._styleModules[stylingEndpointName] = [];
     }
     Gerrit._styleModules[stylingEndpointName].push({
       pluginUrl: this._url,
-      moduleName: moduleName,
+      moduleName,
     });
   };
 
@@ -87,7 +87,7 @@
         Plugin._sharedAPIElement.Element.REPLY_DIALOG));
   };
 
-  var Gerrit = window.Gerrit || {};
+  const Gerrit = window.Gerrit || {};
 
   // Number of plugins to initialize, -1 means 'not yet known'.
   Gerrit._pluginsPending = -1;
@@ -102,12 +102,13 @@
 
   Gerrit.css = function(rulesStr) {
     if (!Gerrit._customStyleSheet) {
-      var styleEl = document.createElement('style');
+      const styleEl = document.createElement('style');
       document.head.appendChild(styleEl);
       Gerrit._customStyleSheet = styleEl.sheet;
     }
 
-    var name = '__pg_js_api_class_' + Gerrit._customStyleSheet.cssRules.length;
+    const name = '__pg_js_api_class_' +
+        Gerrit._customStyleSheet.cssRules.length;
     Gerrit._customStyleSheet.insertRule('.' + name + '{' + rulesStr + '}', 0);
     return name;
   };
@@ -121,9 +122,9 @@
     }
 
     // TODO(andybons): Polyfill currentScript for IE10/11 (edge supports it).
-    var src = opt_src || (document.currentScript &&
+    const src = opt_src || (document.currentScript &&
          document.currentScript.src || document.currentScript.baseURI);
-    var plugin = new Plugin(src);
+    const plugin = new Plugin(src);
     try {
       callback(plugin);
     } catch (e) {
@@ -155,7 +156,7 @@
       if (Gerrit._arePluginsLoaded()) {
         Gerrit._allPluginsPromise = Promise.resolve();
       } else {
-        Gerrit._allPluginsPromise = new Promise(function(resolve) {
+        Gerrit._allPluginsPromise = new Promise(resolve => {
           Gerrit._resolveAllPluginsLoaded = resolve;
         });
       }