diff -u b/core/misc/vertical-tabs.es6.js b/core/misc/vertical-tabs.es6.js
--- b/core/misc/vertical-tabs.es6.js
+++ b/core/misc/vertical-tabs.es6.js
@@ -77,14 +77,14 @@
           .before(tab_list)
           // If there are no visible tab panes, hide the whole vertical-tabs
           // area.
-          .on('updateTabPaneSet', function() {
-            var tab_set = $this.parent();
-            tab_set.show();
-            var $panes = $('> details:visible', this);
-            if ($panes.length == 0) {
-              tab_set.hide();
+          .on('updateTabPaneSet', () => {
+            const tabSet = $this.parent();
+            tabSet.show();
+            const $panes = $('> details:visible', this);
+            if ($panes.length === 0) {
+              tabSet.hide();
             }
-        });
+          });
 
         // Transform each details into a tab.
         $details.each(function () {
@@ -101,10 +101,10 @@
             .attr('open', true)
             .addClass('vertical-tabs__pane')
             // Override the default state:visible handler.
-            .on('state:visible.verticalTabs', function (e) {
-              if (e.target == this && e.trigger) {
+            .on('state:visible.verticalTabs', (e) => {
+              if (e.target === this && e.trigger) {
                 // Get the id of the vertical tab.
-                var id = $(e.target).closest('.form-item, .form-submit, .form-wrapper').attr('id');
+                const id = $(e.target).closest('.form-item, .form-submit, .form-wrapper').attr('id');
                 if (id) {
                   if (!e.value) {
                     if ($(vertical_tab.details.context).is(':visible')) {
@@ -115,7 +115,7 @@
                       vertical_tab.updateSummary();
                     }
                   }
-                  else if(e.value) {
+                  else if (e.value) {
                     vertical_tab.item.show();
                     vertical_tab.updateSummary();
                   }
diff -u b/core/misc/vertical-tabs.js b/core/misc/vertical-tabs.js
--- b/core/misc/vertical-tabs.js
+++ b/core/misc/vertical-tabs.js
@@ -24,6 +24,8 @@
       $('body').once('vertical-tabs-fragments').on('formFragmentLinkClickOrHashChange.verticalTabs', handleFragmentLinkClickOrHashChange);
 
       $(context).find('[data-vertical-tabs-panes]').once('vertical-tabs').each(function () {
+        var _this = this;
+
         var $this = $(this).addClass('vertical-tabs__panes');
         var focusID = $this.find(':hidden.vertical-tabs__active-tab').val();
         var tab_focus = void 0;
@@ -35,15 +37,17 @@
 
         var tab_list = $('<ul class="vertical-tabs__menu"></ul>');
         $this.wrap('<div class="vertical-tabs clearfix"></div>').before(tab_list).on('updateTabPaneSet', function () {
-          var tab_set = $this.parent();
-          tab_set.show();
-          var $panes = $('> details:visible', this);
-          if ($panes.length == 0) {
-            tab_set.hide();
+          var tabSet = $this.parent();
+          tabSet.show();
+          var $panes = $('> details:visible', _this);
+          if ($panes.length === 0) {
+            tabSet.hide();
           }
         });
 
         $details.each(function () {
+          var _this2 = this;
+
           var $that = $(this);
           var vertical_tab = new Drupal.verticalTab({
             title: $that.find('> summary').text(),
@@ -51,7 +55,7 @@
           });
           tab_list.append(vertical_tab.item);
           $that.removeClass('collapsed').attr('open', true).addClass('vertical-tabs__pane').on('state:visible.verticalTabs', function (e) {
-            if (e.target == this && e.trigger) {
+            if (e.target === _this2 && e.trigger) {
               var id = $(e.target).closest('.form-item, .form-submit, .form-wrapper').attr('id');
               if (id) {
                 if (!e.value) {