diff --git a/polygerrit-ui/app/elements/plugins/gr-external-style/gr-external-style.js b/polygerrit-ui/app/elements/plugins/gr-external-style/gr-external-style.js
index 162921ac94..5e3749d62a 100644
--- a/polygerrit-ui/app/elements/plugins/gr-external-style/gr-external-style.js
+++ b/polygerrit-ui/app/elements/plugins/gr-external-style/gr-external-style.js
@@ -21,39 +21,39 @@
       name: String,
     },
 
-    _import: function(url) {
-      return new Promise(function(resolve, reject) {
+    _import(url) {
+      return new Promise((resolve, reject) => {
         this.importHref(url, resolve, reject);
-      }.bind(this));
+      });
     },
 
-    _applyStyle: function(name) {
-      var s = document.createElement('style', 'custom-style');
+    _applyStyle(name) {
+      const s = document.createElement('style', 'custom-style');
       s.setAttribute('include', name);
       Polymer.dom(this.root).appendChild(s);
     },
 
-    ready: function() {
-      Gerrit.awaitPluginsLoaded().then(function() {
-        var sharedStyles = Gerrit._styleModules[this.name];
+    ready() {
+      Gerrit.awaitPluginsLoaded().then(() => {
+        const sharedStyles = Gerrit._styleModules[this.name];
         if (sharedStyles) {
-          var pluginUrls = [];
-          var moduleNames = [];
-          sharedStyles.reduce(function(result, item) {
+          const pluginUrls = [];
+          const moduleNames = [];
+          sharedStyles.reduce((result, item) => {
             if (!result.pluginUrls.includes(item.pluginUrl)) {
               result.pluginUrls.push(item.pluginUrl);
             }
             result.moduleNames.push(item.moduleName);
             return result;
-          }, {pluginUrls: pluginUrls, moduleNames: moduleNames});
+          }, {pluginUrls, moduleNames});
           Promise.all(pluginUrls.map(this._import.bind(this)))
-            .then(function() {
-              moduleNames.forEach(function(name) {
-                this._applyStyle(name);
-              }.bind(this));
-            }.bind(this));
+              .then(() => {
+                for (const name of moduleNames) {
+                  this._applyStyle(name);
+                }
+              });
         }
-      }.bind(this));
+      });
     },
   });
 })();
diff --git a/polygerrit-ui/app/elements/plugins/gr-external-style/gr-external-style_test.html b/polygerrit-ui/app/elements/plugins/gr-external-style/gr-external-style_test.html
index f626f71c54..f0e254f65d 100644
--- a/polygerrit-ui/app/elements/plugins/gr-external-style/gr-external-style_test.html
+++ b/polygerrit-ui/app/elements/plugins/gr-external-style/gr-external-style_test.html
@@ -31,30 +31,30 @@ limitations under the License.
 </test-fixture>
 
 <script>
-  suite('gr-change-metadata integration tests', function() {
-    var sandbox;
-    var element;
+  suite('gr-change-metadata integration tests', () => {
+    let sandbox;
+    let element;
 
-    setup(function(done) {
+    setup(done => {
       sandbox = sinon.sandbox.create();
       sandbox.stub(Gerrit, 'awaitPluginsLoaded').returns(Promise.resolve());
-      Gerrit._styleModules = {'foo': [{pluginUrl: 'bar', moduleName: 'baz',}]};
+      Gerrit._styleModules = {foo: [{pluginUrl: 'bar', moduleName: 'baz'}]};
 
       element = fixture('basic');
       sandbox.stub(element, '_applyStyle');
-      sandbox.stub(element, 'importHref', function(url, resolve) { resolve() });
+      sandbox.stub(element, 'importHref', (url, resolve) => { resolve(); });
       flush(done);
     });
 
-    teardown(function() {
+    teardown(() => {
       sandbox.restore();
     });
 
-    test('imports plugin-provided module', function() {
+    test('imports plugin-provided module', () => {
       assert.isTrue(element.importHref.calledWith('bar'));
     });
 
-    test('applies plugin-provided styles', function() {
+    test('applies plugin-provided styles', () => {
       assert.isTrue(element._applyStyle.calledWith('baz'));
     });
   });
diff --git a/polygerrit-ui/app/elements/plugins/gr-plugin-host/gr-plugin-host.js b/polygerrit-ui/app/elements/plugins/gr-plugin-host/gr-plugin-host.js
index 1c78689897..cd7059ccd4 100644
--- a/polygerrit-ui/app/elements/plugins/gr-plugin-host/gr-plugin-host.js
+++ b/polygerrit-ui/app/elements/plugins/gr-plugin-host/gr-plugin-host.js
@@ -24,28 +24,27 @@
       },
     },
 
-    _configChanged: function(config) {
-      var jsPlugins = config.js_resource_paths || [];
-      var htmlPlugins = config.html_resource_paths || [];
+    _configChanged(config) {
+      const jsPlugins = config.js_resource_paths || [];
+      const htmlPlugins = config.html_resource_paths || [];
       Gerrit._setPluginsCount(jsPlugins.length + htmlPlugins.length);
       this._loadJsPlugins(jsPlugins);
       this._importHtmlPlugins(htmlPlugins);
     },
 
-    _importHtmlPlugins: function(plugins) {
-      plugins.forEach(function(url) {
-        if (url.indexOf('http') !== 0) {
+    _importHtmlPlugins(plugins) {
+      for (let url of plugins) {
+        if (!url.startsWith('http')) {
           url = '/' + url;
         }
         this.importHref(
             url, Gerrit._pluginInstalled, Gerrit._pluginInstalled, true);
-      }.bind(this));
+      }
     },
 
-    _loadJsPlugins: function(plugins) {
-      for (var i = 0; i < plugins.length; i++) {
-        var url = plugins[i];
-        var scriptEl = document.createElement('script');
+    _loadJsPlugins(plugins) {
+      for (let i = 0; i < plugins.length; i++) {
+        const scriptEl = document.createElement('script');
         scriptEl.defer = true;
         scriptEl.src = '/' + plugins[i];
         scriptEl.onerror = Gerrit._pluginInstalled;
diff --git a/polygerrit-ui/app/elements/plugins/gr-plugin-host/gr-plugin-host_test.html b/polygerrit-ui/app/elements/plugins/gr-plugin-host/gr-plugin-host_test.html
index 5965bc3eee..17f4875071 100644
--- a/polygerrit-ui/app/elements/plugins/gr-plugin-host/gr-plugin-host_test.html
+++ b/polygerrit-ui/app/elements/plugins/gr-plugin-host/gr-plugin-host_test.html
@@ -30,22 +30,22 @@ limitations under the License.
 </test-fixture>
 
 <script>
-  suite('gr-diff tests', function() {
-    var element;
-    var sandbox;
+  suite('gr-diff tests', () => {
+    let element;
+    let sandbox;
 
-    setup(function() {
+    setup(() => {
       element = fixture('basic');
       sandbox = sinon.sandbox.create();
       sandbox.stub(document.body, 'appendChild');
       sandbox.stub(element, 'importHref');
     });
 
-    teardown(function() {
+    teardown(() => {
       sandbox.restore();
     });
 
-    test('counts plugins', function() {
+    test('counts plugins', () => {
       sandbox.stub(Gerrit, '_setPluginsCount');
       element.config = {
         html_resource_paths: ['foo/bar', 'baz'],
@@ -54,7 +54,7 @@ limitations under the License.
       assert.isTrue(Gerrit._setPluginsCount.calledWith(3));
     });
 
-    test('imports html plugins from config', function() {
+    test('imports html plugins from config', () => {
       element.config = {
         html_resource_paths: ['foo/bar', 'baz'],
       };