diff --git a/core/modules/block_content/js/block_content.js b/core/modules/block_content/js/block_content.js
index de36d4b..8d4c47b 100644
--- a/core/modules/block_content/js/block_content.js
+++ b/core/modules/block_content/js/block_content.js
@@ -12,13 +12,13 @@
       var $context = $(context);
       $context.find('.block-content-form-revision-information').drupalSetSummary(function (context) {
         var $revisionContext = $(context);
-        var revisionCheckbox = $revisionContext.find('.form-item-revision input');
+        var revisionCheckbox = $revisionContext.find('.js-form-item-revision input');
 
         // Return 'New revision' if the 'Create new revision' checkbox is checked,
         // or if the checkbox doesn't exist, but the revision log does. For users
         // without the "Administer content" permission the checkbox won't appear,
         // but the revision log will if the content type is set to auto-revision.
-        if (revisionCheckbox.is(':checked') || (!revisionCheckbox.length && $revisionContext.find('.form-item-revision-log textarea').length)) {
+        if (revisionCheckbox.is(':checked') || (!revisionCheckbox.length && $revisionContext.find('.js-form-item-revision-log textarea').length)) {
           return Drupal.t('New revision');
         }
 
@@ -28,13 +28,13 @@
       $context.find('fieldset.block-content-translation-options').drupalSetSummary(function (context) {
         var $translationContext = $(context);
         var translate;
-        var $checkbox = $translationContext.find('.form-item-translation-translate input');
+        var $checkbox = $translationContext.find('.js-form-item-translation-translate input');
 
         if ($checkbox.size()) {
           translate = $checkbox.is(':checked') ? Drupal.t('Needs to be updated') : Drupal.t('Does not need to be updated');
         }
         else {
-          $checkbox = $translationContext.find('.form-item-translation-retranslate input');
+          $checkbox = $translationContext.find('.js-form-item-translation-retranslate input');
           translate = $checkbox.is(':checked') ? Drupal.t('Flag other translations as outdated') : Drupal.t('Do not flag other translations as outdated');
         }
 
diff --git a/core/modules/ckeditor/js/ckeditor.admin.js b/core/modules/ckeditor/js/ckeditor.admin.js
index ff75541..260430c 100644
--- a/core/modules/ckeditor/js/ckeditor.admin.js
+++ b/core/modules/ckeditor/js/ckeditor.admin.js
@@ -16,7 +16,7 @@
         var $textarea = $configurationForm
           // Hide the textarea that contains the serialized representation of the
           // CKEditor configuration.
-          .find('.form-item-editor-settings-toolbar-button-groups')
+          .find('.js-form-item-editor-settings-toolbar-button-groups')
           .hide()
           // Return the textarea child node from this expression.
           .find('textarea');
diff --git a/core/modules/comment/comment-entity-form.js b/core/modules/comment/comment-entity-form.js
index b41ab84..6e639bc 100644
--- a/core/modules/comment/comment-entity-form.js
+++ b/core/modules/comment/comment-entity-form.js
@@ -11,7 +11,7 @@
     attach: function (context) {
       var $context = $(context);
       $context.find('fieldset.comment-entity-settings-form').drupalSetSummary(function (context) {
-        return Drupal.checkPlain($(context).find('.form-item-comment input:checked').next('label').text());
+        return Drupal.checkPlain($(context).find('.js-form-item-comment input:checked').next('label').text());
       });
     }
   };
diff --git a/core/modules/field_ui/field_ui.js b/core/modules/field_ui/field_ui.js
index 3ee0dab..aaf6b41 100644
--- a/core/modules/field_ui/field_ui.js
+++ b/core/modules/field_ui/field_ui.js
@@ -16,9 +16,9 @@
         // "re-use existing" can never be filled and submitted at the same time.
         // The actual validation will happen server-side.
         $form.find(
-          '.form-item-label label,' +
-          '.form-item-field-name label,' +
-          '.form-item-existing-storage-label label')
+          '.js-form-item-label label,' +
+          '.js-form-item-field-name label,' +
+          '.js-form-item-existing-storage-label label')
           .addClass('form-required');
 
         var $newFieldType = $form.find('select[name="new_storage_type"]');
diff --git a/core/modules/menu_ui/menu_ui.js b/core/modules/menu_ui/menu_ui.js
index 36fb1d6..87d443e 100644
--- a/core/modules/menu_ui/menu_ui.js
+++ b/core/modules/menu_ui/menu_ui.js
@@ -6,8 +6,8 @@
     attach: function (context) {
       $(context).find('.menu-link-form').drupalSetSummary(function (context) {
         var $context = $(context);
-        if ($context.find('.form-item-menu-enabled input').is(':checked')) {
-          return Drupal.checkPlain($context.find('.form-item-menu-title input').val());
+        if ($context.find('.js-form-item-menu-enabled input').is(':checked')) {
+          return Drupal.checkPlain($context.find('.js-form-item-menu-title input').val());
         }
         else {
           return Drupal.t('Not in menu');
@@ -26,9 +26,9 @@
         var $this = $(this);
         // Try to find menu settings widget elements as well as a 'title' field in
         // the form, but play nicely with user permissions and form alterations.
-        var $checkbox = $this.find('.form-item-menu-enabled input');
-        var $link_title = $context.find('.form-item-menu-title input');
-        var $title = $this.closest('form').find('.form-item-title-0-value input');
+        var $checkbox = $this.find('.js-form-item-menu-enabled input');
+        var $link_title = $context.find('.js-form-item-menu-title input');
+        var $title = $this.closest('form').find('.js-form-item-title-0-value input');
         // Bail out if we do not have all required fields.
         if (!($checkbox.length && $link_title.length && $title.length)) {
           return;
diff --git a/core/modules/node/content_types.js b/core/modules/node/content_types.js
index c77a2c3..6c4e3dd 100644
--- a/core/modules/node/content_types.js
+++ b/core/modules/node/content_types.js
@@ -29,7 +29,7 @@
       $('#edit-language', context).drupalSetSummary(function (context) {
         var vals = [];
 
-        vals.push($(".form-item-language-configuration-langcode select option:selected", context).text());
+        vals.push($(".js-form-item-language-configuration-langcode select option:selected", context).text());
 
         $('input:checked', context).next('label').each(function () {
           vals.push(Drupal.checkPlain($(this).text()));
diff --git a/core/modules/node/node.js b/core/modules/node/node.js
index 60db08f..67f350e 100644
--- a/core/modules/node/node.js
+++ b/core/modules/node/node.js
@@ -12,13 +12,13 @@
       var $context = $(context);
       $context.find('.node-form-revision-information').drupalSetSummary(function (context) {
         var $revisionContext = $(context);
-        var revisionCheckbox = $revisionContext.find('.form-item-revision input');
+        var revisionCheckbox = $revisionContext.find('.js-form-item-revision input');
 
         // Return 'New revision' if the 'Create new revision' checkbox is checked,
         // or if the checkbox doesn't exist, but the revision log does. For users
         // without the "Administer content" permission the checkbox won't appear,
         // but the revision log will if the content type is set to auto-revision.
-        if (revisionCheckbox.is(':checked') || (!revisionCheckbox.length && $revisionContext.find('.form-item-revision-log textarea').length)) {
+        if (revisionCheckbox.is(':checked') || (!revisionCheckbox.length && $revisionContext.find('.js-form-item-revision-log textarea').length)) {
           return Drupal.t('New revision');
         }
 
@@ -52,13 +52,13 @@
       $context.find('fieldset.node-translation-options').drupalSetSummary(function (context) {
         var $translationContext = $(context);
         var translate;
-        var $checkbox = $translationContext.find('.form-item-translation-translate input');
+        var $checkbox = $translationContext.find('.js-form-item-translation-translate input');
 
         if ($checkbox.size()) {
           translate = $checkbox.is(':checked') ? Drupal.t('Needs to be updated') : Drupal.t('Does not need to be updated');
         }
         else {
-          $checkbox = $translationContext.find('.form-item-translation-retranslate input');
+          $checkbox = $translationContext.find('.js-form-item-translation-retranslate input');
           translate = $checkbox.is(':checked') ? Drupal.t('Flag other translations as outdated') : Drupal.t('Do not flag other translations as outdated');
         }
 
diff --git a/core/modules/path/path.js b/core/modules/path/path.js
index aa91bb2..29a8543 100644
--- a/core/modules/path/path.js
+++ b/core/modules/path/path.js
@@ -9,7 +9,7 @@
   Drupal.behaviors.pathDetailsSummaries = {
     attach: function (context) {
       $(context).find('.path-form').drupalSetSummary(function (context) {
-        var path = $('.form-item-path-0-alias input').val();
+        var path = $('.js-form-item-path-0-alias input').val();
 
         return path ?
           Drupal.t('Alias: @alias', {'@alias': path}) :
diff --git a/core/modules/system/src/Tests/Form/ElementsLabelsTest.php b/core/modules/system/src/Tests/Form/ElementsLabelsTest.php
index db5dbee..237391c 100644
--- a/core/modules/system/src/Tests/Form/ElementsLabelsTest.php
+++ b/core/modules/system/src/Tests/Form/ElementsLabelsTest.php
@@ -71,7 +71,7 @@ function testFormLabels() {
     $elements = $this->xpath('//label[@for="edit-form-textfield-test-title-no-show"]');
     $this->assertFalse(isset($elements[0]), 'No label tag when title set not to display.');
 
-    $elements = $this->xpath('//div[contains(@class, "form-item-form-textfield-test-title-invisible") and contains(@class, "form-no-label")]');
+    $elements = $this->xpath('//div[contains(@class, "js-form-item-form-textfield-test-title-invisible") and contains(@class, "form-no-label")]');
     $this->assertTrue(isset($elements[0]), 'Field class is form-no-label when there is no label.');
 
     // Check #field_prefix and #field_suffix placement.
@@ -82,10 +82,10 @@ function testFormLabels() {
     $this->assertTrue(isset($elements[0]), 'Properly places the #field_suffix element immediately after the form field.');
 
     // Check #prefix and #suffix placement.
-    $elements = $this->xpath('//div[@id="form-test-textfield-title-prefix"]/following-sibling::div[contains(@class, \'form-item-form-textfield-test-title\')]');
+    $elements = $this->xpath('//div[@id="form-test-textfield-title-prefix"]/following-sibling::div[contains(@class, \'js-form-item-form-textfield-test-title\')]');
     $this->assertTrue(isset($elements[0]), 'Properly places the #prefix element before the form item.');
 
-    $elements = $this->xpath('//div[@id="form-test-textfield-title-suffix"]/preceding-sibling::div[contains(@class, \'form-item-form-textfield-test-title\')]');
+    $elements = $this->xpath('//div[@id="form-test-textfield-title-suffix"]/preceding-sibling::div[contains(@class, \'js-form-item-form-textfield-test-title\')]');
     $this->assertTrue(isset($elements[0]), 'Properly places the #suffix element before the form item.');
 
     // Check title attribute for radios and checkboxes.
diff --git a/core/modules/system/src/Tests/Form/RebuildTest.php b/core/modules/system/src/Tests/Form/RebuildTest.php
index e993b49..73cd109 100644
--- a/core/modules/system/src/Tests/Form/RebuildTest.php
+++ b/core/modules/system/src/Tests/Form/RebuildTest.php
@@ -109,7 +109,7 @@ function testPreserveFormActionAfterAJAX() {
 
     // Ensure that the form contains two items in the multi-valued field, so we
     // know we're testing a form that was correctly retrieved from cache.
-    $this->assert(count($this->xpath('//form[contains(@id, "node-page-form")]//div[contains(@class, "form-item-field-ajax-test")]//input[@type="text"]')) == 2, 'Form retained its state from cache.');
+    $this->assert(count($this->xpath('//form[contains(@id, "node-page-form")]//div[contains(@class, "js-form-item-field-ajax-test")]//input[@type="text"]')) == 2, 'Form retained its state from cache.');
 
     // Ensure that the form's action is correct.
     $forms = $this->xpath('//form[contains(@class, "node-page-form")]');
diff --git a/core/modules/system/templates/form-element.html.twig b/core/modules/system/templates/form-element.html.twig
index a961801..0887466 100644
--- a/core/modules/system/templates/form-element.html.twig
+++ b/core/modules/system/templates/form-element.html.twig
@@ -49,7 +49,7 @@
   set classes = [
     'form-item',
     'form-type-' ~ type|clean_class,
-    'form-item-' ~ name|clean_class,
+    'js-form-item-' ~ name|clean_class,
     title_display not in ['after', 'before'] ? 'form-no-label',
     disabled == 'disabled' ? 'form-disabled',
   ]
diff --git a/core/modules/views_ui/js/views-admin.js b/core/modules/views_ui/js/views-admin.js
index 7f217dc..dd7b604 100644
--- a/core/modules/views_ui/js/views-admin.js
+++ b/core/modules/views_ui/js/views-admin.js
@@ -432,7 +432,7 @@
       }
       var $context = $(context);
       var $table = $context.find('#views-rearrange-filters').once('views-rearrange-filters');
-      var $operator = $context.find('.form-item-filter-groups-operator').once('views-rearrange-filters');
+      var $operator = $context.find('.js-form-item-filter-groups-operator').once('views-rearrange-filters');
       if ($table.length) {
         new Drupal.viewsUi.RearrangeFilterHandler($table, $operator);
       }
@@ -775,7 +775,7 @@
   Drupal.behaviors.viewsFilterConfigSelectAll = {
     attach: function (context) {
       // Show the select all checkbox.
-      $(context).find('#views-ui-handler-form div.form-item-options-value-all').once('filterConfigSelectAll')
+      $(context).find('#views-ui-handler-form div.js-form-item-options-value-all').once('filterConfigSelectAll')
         .show()
         .find('input[type=checkbox]')
         .on('click', function () {
@@ -786,7 +786,7 @@
           });
         });
       // Uncheck the select all checkbox if any of the others are unchecked.
-      $('#views-ui-handler-form').find('div.form-type-checkbox').not($('.form-item-options-value-all'))
+      $('#views-ui-handler-form').find('div.js-form-type-checkbox').not($('.js-form-item-options-value-all'))
         .find('input[type=checkbox]')
         .on('click', function () {
           if ($(this).is('checked') === false) {
diff --git a/core/themes/classy/templates/form/form-element.html.twig b/core/themes/classy/templates/form/form-element.html.twig
index cf54c20..8b316c8 100644
--- a/core/themes/classy/templates/form/form-element.html.twig
+++ b/core/themes/classy/templates/form/form-element.html.twig
@@ -47,6 +47,7 @@
   set classes = [
     'form-item',
     'form-type-' ~ type|clean_class,
+    'js-form-item-' ~ name|clean_class,
     'form-item-' ~ name|clean_class,
     title_display not in ['after', 'before'] ? 'form-no-label',
     disabled == 'disabled' ? 'form-disabled',