diff --git a/core/modules/media_library/js/media_library.click_to_select.es6.js b/core/modules/media_library/js/media_library.click_to_select.es6.js
index 90c58b665b..db42fe4790 100644
--- a/core/modules/media_library/js/media_library.click_to_select.es6.js
+++ b/core/modules/media_library/js/media_library.click_to_select.es6.js
@@ -5,6 +5,11 @@
 (($, Drupal) => {
   /**
    * Allows users to select an element which checks a hidden checkbox.
+   *
+   * @type {Drupal~behavior}
+   *
+   * @prop {Drupal~behaviorAttach} attach
+   *   Attaches behavior for selecting media library item.
    */
   Drupal.behaviors.ClickToSelect = {
     attach(context) {
diff --git a/core/modules/media_library/js/media_library.ui.es6.js b/core/modules/media_library/js/media_library.ui.es6.js
index df22ff0676..ad457aee12 100644
--- a/core/modules/media_library/js/media_library.ui.es6.js
+++ b/core/modules/media_library/js/media_library.ui.es6.js
@@ -17,6 +17,11 @@
 
   /**
    * Warn users when clicking outgoing links from the library or widget.
+   *
+   * @type {Drupal~behavior}
+   *
+   * @prop {Drupal~behaviorAttach} attach
+   *   Attaches behavior to links in the media library.
    */
   Drupal.behaviors.MediaLibraryWidgetWarn = {
     attach(context) {
@@ -42,13 +47,18 @@
    * want to load the changed library content. This is not only more efficient,
    * but also provides a more accessible user experience for screen readers.
    *
+   * @type {Drupal~behavior}
+   *
+   * @prop {Drupal~behaviorAttach} attach
+   *   Attaches behavior to vertical tabs in the media library.
+   *
    * @todo Remove when the AJAX system adds support for replacing a specific
    *   selector via a link.
    *   https://www.drupal.org/project/drupal/issues/3026636
    */
   Drupal.behaviors.MediaLibraryTabs = {
     attach(context) {
-      const $menu = $('.media-library-menu');
+      const $menu = $('.js-media-library-menu');
       $menu
         .find('a', context)
         .once('media-library-menu-item')
@@ -110,35 +120,17 @@
     },
   };
 
-  /**
-   * Update the number of selected items in the button pane.
-   */
-  function updateSelectionInfo(remaining) {
-    const $buttonPane = $('.media-library-widget-modal .ui-dialog-buttonpane');
-    if (!$buttonPane.length) {
-      return;
-    }
-
-    // Add the selection count.
-    const latestCount = Drupal.theme(
-      'mediaLibrarySelectionCount',
-      Drupal.MediaLibrary.currentSelection,
-      remaining,
-    );
-    const $existingCount = $buttonPane.find('.media-library-selected-count');
-    if ($existingCount.length) {
-      $existingCount.replaceWith(latestCount);
-    } else {
-      $buttonPane.append(latestCount);
-    }
-  }
-
   /**
    * Update the media library selection when loaded or media items are selected.
+   *
+   * @type {Drupal~behavior}
+   *
+   * @prop {Drupal~behaviorAttach} attach
+   *   Attaches behavior to select media items.
    */
   Drupal.behaviors.MediaLibraryItemSelection = {
     attach(context, settings) {
-      const $form = $('.media-library-views-form', context);
+      const $form = $('.js-media-library-views-form', context);
       const currentSelection = Drupal.MediaLibrary.currentSelection;
 
       if (!$form.length) {
@@ -167,13 +159,19 @@
           currentSelection.splice(position, 1);
         }
 
-        // Set the selection  in the hidden form element.
+        // Set the selection in the hidden form element.
         $form
-          .find('input#media-library-modal-selection')
+          .find('#media-library-modal-selection')
           .val(currentSelection.join())
           .trigger('change');
       });
 
+      /**
+       * Disable media items.
+       *
+       * @param {jQuery} $items
+       *   A jQuery object representing the media items that should be disabled.
+       */
       function disableItems($items) {
         $items
           .prop('disabled', true)
@@ -181,6 +179,12 @@
           .addClass('media-library-item--disabled');
       }
 
+      /**
+       * Enable media items.
+       *
+       * @param {jQuery} $items
+       *   A jQuery object representing the media items that should be enabled.
+       */
       function enableItems($items) {
         $items
           .prop('disabled', false)
@@ -188,8 +192,34 @@
           .removeClass('media-library-item--disabled');
       }
 
+      /**
+       * Update the number of selected items in the button pane.
+       *
+       * @param {number} remaining
+       *   The number of remaining slots.
+       */
+      function updateSelectionInfo(remaining) {
+        const $buttonPane = $('.media-library-widget-modal .ui-dialog-buttonpane');
+        if (!$buttonPane.length) {
+          return;
+        }
+
+        // Add the selection count.
+        const latestCount = Drupal.theme(
+          'mediaLibrarySelectionCount',
+          Drupal.MediaLibrary.currentSelection,
+          remaining,
+        );
+        const $existingCount = $buttonPane.find('.media-library-selected-count');
+        if ($existingCount.length) {
+          $existingCount.replaceWith(latestCount);
+        } else {
+          $buttonPane.append(latestCount);
+        }
+      }
+
       // The hidden selection form field changes when the selection is updated.
-      $('input#media-library-modal-selection', $form)
+      $('#media-library-modal-selection', $form)
         .once('media-library-selection-change')
         .on('change', e => {
           updateSelectionInfo(settings.media_library.selection_remaining);
@@ -228,6 +258,11 @@
 
   /**
    * Clear the current selection.
+   *
+   * @type {Drupal~behavior}
+   *
+   * @prop {Drupal~behaviorAttach} attach
+   *   Attaches behavior to clear the selection when the library modal closes.
    */
   Drupal.behaviors.MediaLibraryModalClearSelection = {
     attach() {
diff --git a/core/modules/media_library/js/media_library.ui.js b/core/modules/media_library/js/media_library.ui.js
index af324857bf..3b1a8a2ee1 100644
--- a/core/modules/media_library/js/media_library.ui.js
+++ b/core/modules/media_library/js/media_library.ui.js
@@ -24,7 +24,7 @@
 
   Drupal.behaviors.MediaLibraryTabs = {
     attach: function attach(context) {
-      var $menu = $('.media-library-menu');
+      var $menu = $('.js-media-library-menu');
       $menu.find('a', context).once('media-library-menu-item').on('click', function (e) {
         e.preventDefault();
         e.stopPropagation();
@@ -69,24 +69,9 @@
     }
   };
 
-  function updateSelectionInfo(remaining) {
-    var $buttonPane = $('.media-library-widget-modal .ui-dialog-buttonpane');
-    if (!$buttonPane.length) {
-      return;
-    }
-
-    var latestCount = Drupal.theme('mediaLibrarySelectionCount', Drupal.MediaLibrary.currentSelection, remaining);
-    var $existingCount = $buttonPane.find('.media-library-selected-count');
-    if ($existingCount.length) {
-      $existingCount.replaceWith(latestCount);
-    } else {
-      $buttonPane.append(latestCount);
-    }
-  }
-
   Drupal.behaviors.MediaLibraryItemSelection = {
     attach: function attach(context, settings) {
-      var $form = $('.media-library-views-form', context);
+      var $form = $('.js-media-library-views-form', context);
       var currentSelection = Drupal.MediaLibrary.currentSelection;
 
       if (!$form.length) {
@@ -107,7 +92,7 @@
           currentSelection.splice(position, 1);
         }
 
-        $form.find('input#media-library-modal-selection').val(currentSelection.join()).trigger('change');
+        $form.find('#media-library-modal-selection').val(currentSelection.join()).trigger('change');
       });
 
       function disableItems($items) {
@@ -118,7 +103,22 @@
         $items.prop('disabled', false).closest('.js-media-library-item').removeClass('media-library-item--disabled');
       }
 
-      $('input#media-library-modal-selection', $form).once('media-library-selection-change').on('change', function (e) {
+      function updateSelectionInfo(remaining) {
+        var $buttonPane = $('.media-library-widget-modal .ui-dialog-buttonpane');
+        if (!$buttonPane.length) {
+          return;
+        }
+
+        var latestCount = Drupal.theme('mediaLibrarySelectionCount', Drupal.MediaLibrary.currentSelection, remaining);
+        var $existingCount = $buttonPane.find('.media-library-selected-count');
+        if ($existingCount.length) {
+          $existingCount.replaceWith(latestCount);
+        } else {
+          $buttonPane.append(latestCount);
+        }
+      }
+
+      $('#media-library-modal-selection', $form).once('media-library-selection-change').on('change', function (e) {
         updateSelectionInfo(settings.media_library.selection_remaining);
 
         if (currentSelection.length === settings.media_library.selection_remaining) {
diff --git a/core/modules/media_library/js/media_library.view.es6.js b/core/modules/media_library/js/media_library.view.es6.js
index dcda58d62e..be2ddf390a 100644
--- a/core/modules/media_library/js/media_library.view.es6.js
+++ b/core/modules/media_library/js/media_library.view.es6.js
@@ -4,11 +4,16 @@
 (($, Drupal) => {
   /**
    * Adds hover effect to media items.
+   *
+   * @type {Drupal~behavior}
+   *
+   * @prop {Drupal~behaviorAttach} attach
+   *   Attaches behavior to add a class when hovering over media items.
    */
   Drupal.behaviors.MediaLibraryHover = {
     attach(context) {
       $(
-        '.media-library-item .js-click-to-select-trigger,.media-library-item .js-click-to-select-checkbox',
+        '.js-click-to-select-trigger, .js-click-to-select-checkbox',
         context,
       )
         .once('media-library-item-hover')
@@ -22,10 +27,15 @@
 
   /**
    * Adds focus effect to media items.
+   *
+   * @type {Drupal~behavior}
+   *
+   * @prop {Drupal~behaviorAttach} attach
+   *   Attaches behavior to add a focus effect to media items.
    */
   Drupal.behaviors.MediaLibraryFocus = {
     attach(context) {
-      $('.media-library-item .js-click-to-select-checkbox input', context)
+      $('.js-click-to-select-checkbox input', context)
         .once('media-library-item-focus')
         .on('focus blur', ({ currentTarget, type }) => {
           $(currentTarget)
@@ -37,10 +47,15 @@
 
   /**
    * Adds checkbox to select all items in the library.
+   *
+   * @type {Drupal~behavior}
+   *
+   * @prop {Drupal~behaviorAttach} attach
+   *   Attaches behavior to select all media items.
    */
   Drupal.behaviors.MediaLibrarySelectAll = {
     attach(context) {
-      const $view = $('.media-library-view', context).once(
+      const $view = $('.js-media-library-view', context).once(
         'media-library-select-all',
       );
       if ($view.length && $view.find('.media-library-item').length) {
diff --git a/core/modules/media_library/js/media_library.view.js b/core/modules/media_library/js/media_library.view.js
index 18facca93a..73028f6af8 100644
--- a/core/modules/media_library/js/media_library.view.js
+++ b/core/modules/media_library/js/media_library.view.js
@@ -8,7 +8,7 @@
 (function ($, Drupal) {
   Drupal.behaviors.MediaLibraryHover = {
     attach: function attach(context) {
-      $('.media-library-item .js-click-to-select-trigger,.media-library-item .js-click-to-select-checkbox', context).once('media-library-item-hover').on('mouseover mouseout', function (_ref) {
+      $('.js-click-to-select-trigger, .js-click-to-select-checkbox', context).once('media-library-item-hover').on('mouseover mouseout', function (_ref) {
         var currentTarget = _ref.currentTarget,
             type = _ref.type;
 
@@ -19,7 +19,7 @@
 
   Drupal.behaviors.MediaLibraryFocus = {
     attach: function attach(context) {
-      $('.media-library-item .js-click-to-select-checkbox input', context).once('media-library-item-focus').on('focus blur', function (_ref2) {
+      $('.js-click-to-select-checkbox input', context).once('media-library-item-focus').on('focus blur', function (_ref2) {
         var currentTarget = _ref2.currentTarget,
             type = _ref2.type;
 
@@ -30,7 +30,7 @@
 
   Drupal.behaviors.MediaLibrarySelectAll = {
     attach: function attach(context) {
-      var $view = $('.media-library-view', context).once('media-library-select-all');
+      var $view = $('.js-media-library-view', context).once('media-library-select-all');
       if ($view.length && $view.find('.media-library-item').length) {
         var $checkbox = $('<input type="checkbox" class="form-checkbox" />').on('click', function (_ref3) {
           var currentTarget = _ref3.currentTarget;
diff --git a/core/modules/media_library/js/media_library.widget.es6.js b/core/modules/media_library/js/media_library.widget.es6.js
index 63de589b7d..93878a0f6a 100644
--- a/core/modules/media_library/js/media_library.widget.es6.js
+++ b/core/modules/media_library/js/media_library.widget.es6.js
@@ -4,6 +4,11 @@
 (($, Drupal) => {
   /**
    * Allows users to re-order their selection with drag+drop.
+   *
+   * @type {Drupal~behavior}
+   *
+   * @prop {Drupal~behaviorAttach} attach
+   *   Attaches behavior to re-order selected media items.
    */
   Drupal.behaviors.MediaLibraryWidgetSortable = {
     attach(context) {
@@ -30,6 +35,11 @@
 
   /**
    * Allows selection order to be set without drag+drop for accessibility.
+   *
+   * @type {Drupal~behavior}
+   *
+   * @prop {Drupal~behaviorAttach} attach
+   *   Attaches behavior to toggle the weight field for media items.
    */
   Drupal.behaviors.MediaLibraryWidgetToggleWeight = {
     attach(context) {
diff --git a/core/modules/media_library/src/MediaLibraryUiBuilder.php b/core/modules/media_library/src/MediaLibraryUiBuilder.php
index b981602fbb..f4b889bbeb 100644
--- a/core/modules/media_library/src/MediaLibraryUiBuilder.php
+++ b/core/modules/media_library/src/MediaLibraryUiBuilder.php
@@ -151,7 +151,7 @@ protected function buildMediaTypeMenu(MediaLibraryState $state) {
       '#theme' => 'links',
       '#links' => [],
       '#attributes' => [
-        'class' => ['media-library-menu'],
+        'class' => ['media-library-menu', 'js-media-library-menu'],
       ],
     ];
 
diff --git a/core/modules/media_library/src/Plugin/views/field/MediaLibrarySelectForm.php b/core/modules/media_library/src/Plugin/views/field/MediaLibrarySelectForm.php
index 155eaa8401..6ef0f57c16 100644
--- a/core/modules/media_library/src/Plugin/views/field/MediaLibrarySelectForm.php
+++ b/core/modules/media_library/src/Plugin/views/field/MediaLibrarySelectForm.php
@@ -46,6 +46,10 @@ public function render(ResultRow $values) {
    *   The current state of the form.
    */
   public function viewsForm(array &$form, FormStateInterface $form_state) {
+    $form['#attributes'] = [
+      'class' => ['media-library-views-form', 'js-media-library-views-form'],
+    ];
+
     // Render checkboxes for all rows.
     $form[$this->options['id']]['#tree'] = TRUE;
     foreach ($this->view->result as $row_index => $row) {