diff --git a/core/modules/ckeditor/js/ckeditor.admin.js b/core/modules/ckeditor/js/ckeditor.admin.js
index 24ebfb4..d2c5cea 100644
--- a/core/modules/ckeditor/js/ckeditor.admin.js
+++ b/core/modules/ckeditor/js/ckeditor.admin.js
@@ -18,14 +18,14 @@
       var $configurationForm = $(context).find('.ckeditor-toolbar-configuration').once('ckeditor-configuration');
       if ($configurationForm.length) {
         var $textarea = $configurationForm
-          // Hide the textarea that contains the serialized representation of the
-          // CKEditor configuration.
+          // Hide the textarea that contains the serialized representation of
+          // the CKEditor configuration.
           .find('.form-item-editor-settings-toolbar-button-groups')
           .hide()
           // Return the textarea child node from this expression.
           .find('textarea');
 
-        // The HTML for the CKEditor configuration is assembled on the server and
+        // The HTML for the CKEditor configuration is assembled on the server
         // and sent to the client as a serialized DOM fragment.
         $configurationForm.append(drupalSettings.ckeditor.toolbarAdmin);
 
@@ -50,15 +50,16 @@
       }
     },
     detach: function (context, settings, trigger) {
-      // Early-return if the trigger for detachment is something else than unload.
+      // Early-return if the trigger for detachment is something else than
+      // unload.
       if (trigger !== 'unload') {
         return;
       }
 
       // We're detaching because CKEditor as text editor has been disabled; this
-      // really means that all CKEditor toolbar buttons have been removed. Hence,
-      // all editor features will be removed, so any reactions from filters will
-      // be undone.
+      // really means that all CKEditor toolbar buttons have been removed.
+      // Hence,all editor features will be removed, so any reactions from
+      // filters will be undone.
       var $configurationForm = $(context).find('.ckeditor-toolbar-configuration').findOnce('ckeditor-configuration');
       if ($configurationForm.length && Drupal.ckeditor.models && Drupal.ckeditor.models.Model) {
         var config = Drupal.ckeditor.models.Model.toJSON().activeEditorConfig;
@@ -93,20 +94,22 @@
     models: {},
 
     /**
-     * Translates a change in CKEditor config DOM structure into the config model.
+     * Translates a change in CKEditor config DOM structure into the config
+     *   model.
      *
-     * If the button is moved within an existing group, the DOM structure is simply
-     * translated to a configuration model. If the button is moved into a new group
-     * placeholder, then a process is launched to name that group before the button
-     * move is translated into configuration.
+     * If the button is moved within an existing group, the DOM structure is
+     * simply translated to a configuration model. If the button is moved into a
+     * new group placeholder, then a process is launched to name that group
+     * before the button move is translated into configuration.
      *
      * @param {Backbone.View} view
      *   The Backbone View that invoked this function.
      * @param {jQuery} $button
      *   A jQuery set that contains an li element that wraps a button element.
      * @param {function} callback
-     *   A callback to invoke after the button group naming modal dialog has been
-     *   closed.
+     *   A callback to invoke after the button group naming modal dialog has
+     *   been closed.
+     *
      */
     registerButtonMove: function (view, $button, callback) {
       var $group = $button.closest('.ckeditor-toolbar-group');
@@ -127,10 +130,12 @@
     },
 
     /**
-     * Translates a change in CKEditor config DOM structure into the config model.
+     * Translates a change in CKEditor config DOM structure into the config
+     *   model.
      *
-     * Each row has a placeholder group at the end of the row. A user may not move
-     * an existing button group past the placeholder group at the end of a row.
+     * Each row has a placeholder group at the end of the row. A user may not
+     * move an existing button group past the placeholder group at the end of a
+     * row.
      *
      * @param {Backbone.View} view
      *   The Backbone View that invoked this function.
@@ -155,15 +160,16 @@
     },
 
     /**
-     * Opens a Drupal dialog with a form for changing the title of a button group.
+     * Opens a Drupal dialog with a form for changing the title of a button
+     *   group.
      *
      * @param {Backbone.View} view
      *   The Backbone View that invoked this function.
      * @param {jQuery} $group
      *   A jQuery set that contains an li element that wraps a group of buttons.
      * @param {function} callback
-     *   A callback to invoke after the button group naming modal dialog has been
-     *   closed.
+     *   A callback to invoke after the button group naming modal dialog has
+     *   been closed.
      */
     openGroupNameDialog: function (view, $group, callback) {
       callback = callback || function () {};
@@ -172,8 +178,8 @@
        * Validates the string provided as a button group title.
        *
        * @param {HTMLElement} form
-       *   The form DOM element that contains the input with the new button group
-       *   title string.
+       *   The form DOM element that contains the input with the new button
+       *   group title string.
        *
        * @return {bool}
        *   Returns true when an error exists, otherwise returns false.
@@ -200,8 +206,8 @@
        * @param {string} action
        *   The dialog action chosen by the user: 'apply' or 'cancel'.
        * @param {HTMLElement} form
-       *   The form DOM element that contains the input with the new button group
-       *   title string.
+       *   The form DOM element that contains the input with the new button
+       *   group title string.
        */
       function closeDialog(action, form) {
 
@@ -211,7 +217,8 @@
         function shutdown() {
           dialog.close(action);
 
-          // The processing marker can be deleted since the dialog has been closed.
+          // The processing marker can be deleted since the dialog has been
+          // closed.
           delete view.isProcessing;
         }
 
@@ -219,13 +226,14 @@
          * Applies a string as the name of a CKEditor button group.
          *
          * @param {jQuery} $group
-         *   A jQuery set that contains an li element that wraps a group of buttons.
+         *   A jQuery set that contains an li element that wraps a group of
+         *   buttons.
          * @param {string} name
          *   The new name of the CKEditor button group.
          */
         function namePlaceholderGroup($group, name) {
-          // If it's currently still a placeholder, then that means we're creating
-          // a new group, and we must do some extra work.
+          // If it's currently still a placeholder, then that means we're
+          // creating a new group, and we must do some extra work.
           if ($group.hasClass('placeholder')) {
             // Remove all whitespace from the name, lowercase it and ensure
             // HTML-safe encoding, then use this as the group ID for CKEditor
@@ -338,12 +346,13 @@
           $(event.target).remove();
         }
       });
-      // A modal dialog is used because the user must provide a button group name
-      // or cancel the button placement before taking any other action.
+      // A modal dialog is used because the user must provide a button group
+      // name or cancel the button placement before taking any other action.
       dialog.showModal();
 
       $(document.querySelector('.ckeditor-name-toolbar-group').querySelector('input'))
-        // When editing, set the "group name" input in the form to the current value.
+        // When editing, set the "group name" input in the form to the current
+        // value.
         .attr('value', $group.attr('data-drupal-ckeditor-toolbar-group-name'))
         // Focus on the "group name" input in the form.
         .trigger('focus');
@@ -374,10 +383,11 @@
           $this.data('ckeditorButtonPluginSettingsActiveButtons', []);
         });
 
-        // Whenever a button is added or removed, check if we should show or hide
-        // the corresponding plugin settings. (Note that upon initialization, each
-        // button that already is part of the toolbar still is considered "added",
-        // hence it also works correctly for buttons that were added previously.)
+        // Whenever a button is added or removed, check if we should show or
+        // hide the corresponding plugin settings. (Note that upon
+        // initialization, each button that already is part of the toolbar still
+        // is considered "added", hence it also works correctly for buttons that
+        // were added previously.)
         $context
           .find('.ckeditor-toolbar-active')
           .off('CKEditorToolbarChanged.ckeditorAdminPluginSettings')
@@ -428,6 +438,7 @@
    * Themes a blank CKEditor row.
    *
    * @return {string}
+   *   A HTML string for a CKEditor row.
    */
   Drupal.theme.ckeditorRow = function () {
     return '<li class="ckeditor-row placeholder" role="group"><ul class="ckeditor-toolbar-groups clearfix"></ul></li>';
@@ -437,6 +448,7 @@
    * Themes a blank CKEditor button group.
    *
    * @return {string}
+   *   A HTML string for a CKEditor button group.
    */
   Drupal.theme.ckeditorToolbarGroup = function () {
     var group = '';
@@ -451,6 +463,7 @@
    * Themes a form for changing the title of a CKEditor button group.
    *
    * @return {string}
+   *   A HTML string for the form for the title of a CKEditor button group.
    */
   Drupal.theme.ckeditorButtonGroupNameForm = function () {
     return '<form><input name="group-name" required="required"></form>';
@@ -460,6 +473,7 @@
    * Themes a button that will toggle the button group names in active config.
    *
    * @return {string}
+   *   A HTML string for the button to toggle group names.
    */
   Drupal.theme.ckeditorButtonGroupNamesToggle = function () {
     return '<a class="ckeditor-groupnames-toggle" role="button" aria-pressed="false"></a>';
@@ -469,6 +483,7 @@
    * Themes a button that will prompt the user to name a new button group.
    *
    * @return {string}
+   *   A HTML string for the button to create a name for a new button group.
    */
   Drupal.theme.ckeditorNewButtonGroup = function () {
     return '<li class="ckeditor-add-new-group"><button role="button" aria-label="' + Drupal.t('Add a CKEditor button group to the end of this row.') + '">' + Drupal.t('Add group') + '</button></li>';
diff --git a/core/modules/ckeditor/js/ckeditor.js b/core/modules/ckeditor/js/ckeditor.js
index 4cc77aa..7ad9cd5 100644
--- a/core/modules/ckeditor/js/ckeditor.js
+++ b/core/modules/ckeditor/js/ckeditor.js
@@ -16,9 +16,12 @@
      * Editor attach callback.
      *
      * @param {HTMLElement} element
+     *   The element to attach the editor to.
      * @param {string} format
+     *   The text format for the editor.
      *
      * @return {bool}
+     *   The result of the editor attach function.
      */
     attach: function (element, format) {
       this._loadExternalPlugins(format);
@@ -46,10 +49,14 @@
      * Editor detach callback.
      *
      * @param {HTMLElement} element
+     *   The element to detach the editor from.
      * @param {string} format
+     *   The text format used for the editor.
      * @param {string} trigger
+     *   The event trigger for the detach.
      *
      * @return {bool}
+     *   The result of the detach function.
      */
     detach: function (element, format, trigger) {
       var editor = CKEDITOR.dom.element.get(element).getEditor();
@@ -66,11 +73,15 @@
     },
 
     /**
+     * Reacts on a change in the editor element.
      *
      * @param {HTMLElement} element
+     *   The element where the change occured.
      * @param {function} callback
+     *   Callback called with the value of the editor.
      *
      * @return {bool}
+     *   The result of the onChange function.
      */
     onChange: function (element, callback) {
       var editor = CKEDITOR.dom.element.get(element).getEditor();
@@ -83,13 +94,19 @@
     },
 
     /**
+     * Attaches an inline editor to a DOM element.
      *
      * @param {HTMLElement} element
+     *   The element to attach the editor to.
      * @param {object} format
-     * @param {string} mainToolbarId
-     * @param {string} floatedToolbarId
+     *   The text format used in the editor.
+     * @param {string} [mainToolbarId]
+     *   The id attribute for the main editor toolbar, if any.
+     * @param {string} [floatedToolbarId]
+     *   The id attribute for the floated editor toolbar, if any.
      *
      * @return {bool}
+     *   The result of the attachInlineEditor function.
      */
     attachInlineEditor: function (element, format, mainToolbarId, floatedToolbarId) {
       this._loadExternalPlugins(format);
@@ -143,7 +160,10 @@
     },
 
     /**
+     * Loads the required external plugins for the editor.
+     *
      * @param {object} format
+     *   The text format used in the editor.
      */
     _loadExternalPlugins: function (format) {
       var externalPlugins = format.editorSettings.drupalExternalPlugins;
diff --git a/core/modules/ckeditor/js/ckeditor.stylescombo.admin.js b/core/modules/ckeditor/js/ckeditor.stylescombo.admin.js
index b73d1b1..fce1067 100644
--- a/core/modules/ckeditor/js/ckeditor.stylescombo.admin.js
+++ b/core/modules/ckeditor/js/ckeditor.stylescombo.admin.js
@@ -11,9 +11,9 @@
    * Ensures that the "stylescombo" button's metadata remains up-to-date.
    *
    * Triggers the CKEditorPluginSettingsChanged event whenever the "stylescombo"
-   * plugin settings change, to ensure that the corresponding feature metadata is
-   * immediately updated — i.e. ensure that HTML tags and classes entered here are
-   * known to be "required", which may affect filter settings.
+   * plugin settings change, to ensure that the corresponding feature metadata
+   * is immediately updated — i.e. ensure that HTML tags and classes entered
+   * here are known to be "required", which may affect filter settings.
    *
    * @type {Drupal~behavior}
    */
@@ -22,10 +22,11 @@
       var $context = $(context);
 
       // React to changes in the list of user-defined styles: calculate the new
-      // stylesSet setting up to 2 times per second, and if it is different, fire
-      // the CKEditorPluginSettingsChanged event with the updated parts of the
-      // CKEditor configuration. (This will, in turn, cause the hidden CKEditor
-      // instance to be updated and a drupalEditorFeatureModified event to fire.)
+      // stylesSet setting up to 2 times per second, and if it is different,
+      // fire the CKEditorPluginSettingsChanged event with the updated parts of
+      // the CKEditor configuration. (This will, in turn, cause the hidden
+      // CKEditor instance to be updated and a drupalEditorFeatureModified event
+      // to fire.)
       var $ckeditorActiveToolbar = $context
         .find('.ckeditor-toolbar-configuration')
         .find('.ckeditor-toolbar-active');
@@ -49,9 +50,9 @@
      *
      * @see \Drupal\ckeditor\Plugin\ckeditor\plugin\StylesCombo::generateStylesSetSetting()
      *
-     * Note that this is a more forgiving implementation than the PHP version: the
-     * parsing works identically, but instead of failing on invalid styles, we
-     * just ignore those.
+     * Note that this is a more forgiving implementation than the PHP version:
+     * the parsing works identically, but instead of failing on invalid styles,
+     * we just ignore those.
      *
      * @param {string} styles
      *   The "styles" setting.
diff --git a/core/modules/ckeditor/js/plugins/drupalimage/plugin.js b/core/modules/ckeditor/js/plugins/drupalimage/plugin.js
index 68eb7fe..2cd6254 100644
--- a/core/modules/ckeditor/js/plugins/drupalimage/plugin.js
+++ b/core/modules/ckeditor/js/plugins/drupalimage/plugin.js
@@ -131,10 +131,10 @@
             // when shifting state, so might deal with a new instance.
             widget = editor.widgets.getByElement(image);
 
-            // It's first edit, just after widget instance creation, but before it was
-            // inserted into DOM. So we need to retrieve the widget wrapper from
-            // inside the DocumentFragment which we cached above and finalize other
-            // things (like ready event and flag).
+            // It's first edit, just after widget instance creation, but before
+            // it was inserted into DOM. So we need to retrieve the widget
+            // wrapper from inside the DocumentFragment which we cached above
+            // and finalize other things (like ready event and flag).
             if (firstEdit) {
               editor.widgets.finalizeCreation(container);
             }
diff --git a/core/modules/ckeditor/js/plugins/drupalimagecaption/plugin.js b/core/modules/ckeditor/js/plugins/drupalimagecaption/plugin.js
index 1dffb23..bee50fc 100644
--- a/core/modules/ckeditor/js/plugins/drupalimagecaption/plugin.js
+++ b/core/modules/ckeditor/js/plugins/drupalimagecaption/plugin.js
@@ -213,7 +213,8 @@
             }
           };
         };
-      }, null, null, 20); // Low priority to ensure drupalimage's event handler runs first.
+      // Low priority to ensure drupalimage's event handler runs first.
+      }, null, null, 20);
     }
   });
 
@@ -224,9 +225,12 @@
    * children in DFS order.
    *
    * @param {CKEDITOR.htmlParser.element} element
+   *   The element to search.
    * @param {string} name
+   *   The element name to search for.
    *
-   * @return {CKEDITOR.htmlParser.element}
+   * @return {?CKEDITOR.htmlParser.element}
+   *   The found element, or null.
    */
   function findElementByName(element, name) {
     if (element.name === name) {
diff --git a/core/modules/ckeditor/js/plugins/drupallink/plugin.js b/core/modules/ckeditor/js/plugins/drupallink/plugin.js
index c26445b..f4dd094 100644
--- a/core/modules/ckeditor/js/plugins/drupallink/plugin.js
+++ b/core/modules/ckeditor/js/plugins/drupallink/plugin.js
@@ -32,14 +32,14 @@
             for (var attrIndex = 0; attrIndex < linkDOMElement.attributes.length; attrIndex++) {
               attribute = linkDOMElement.attributes.item(attrIndex);
               attributeName = attribute.nodeName.toLowerCase();
-              // Don't consider data-cke-saved- attributes; they're just there to
-              // work around browser quirks.
+              // Don't consider data-cke-saved- attributes; they're just there
+              // to work around browser quirks.
               if (attributeName.substring(0, 15) === 'data-cke-saved-') {
                 continue;
               }
               // Store the value for this attribute, unless there's a
-              // data-cke-saved- alternative for it, which will contain the quirk-
-              // free, original value.
+              // data-cke-saved- alternative for it, which will contain the
+              // quirk-free, original value.
               existingValues[attributeName] = linkElement.data('cke-saved-' + attributeName) || attribute.nodeValue;
             }
           }
@@ -97,8 +97,8 @@
             editor.fire('saveSnapshot');
           };
           // Drupal.t() will not work inside CKEditor plugins because CKEditor
-          // loads the JavaScript file instead of Drupal. Pull translated strings
-          // from the plugin settings that are translated server-side.
+          // loads the JavaScript file instead of Drupal. Pull translated
+          // strings from the plugin settings that are translated server-side.
           var dialogSettings = {
             title: linkElement ? editor.config.drupalLink_dialogTitleEdit : editor.config.drupalLink_dialogTitleAdd,
             dialogClass: 'editor-link-dialog'
@@ -210,8 +210,11 @@
    *  [<a href="#"><b>li]nk</b></a>
    *
    * @param {CKEDITOR.editor} editor
+   *   The ckeditor editor object
+   *
+   * @return {?HTMLElement}
+   *   The selected link element, or null.
    *
-   * @return {?bool}
    */
   function getSelectedLink(editor) {
     var selection = editor.getSelection();
diff --git a/core/modules/ckeditor/js/views/AuralView.js b/core/modules/ckeditor/js/views/AuralView.js
index 439e8dd..68d4a24 100644
--- a/core/modules/ckeditor/js/views/AuralView.js
+++ b/core/modules/ckeditor/js/views/AuralView.js
@@ -1,6 +1,7 @@
 /**
  * @file
- * A Backbone View that provides the aural view of CKEditor toolbar configuration.
+ * A Backbone View that provides the aural view of CKEditor toolbar
+ *   configuration.
  */
 
 (function (Drupal, Backbone, $) {
@@ -37,6 +38,7 @@
      * Calls announce on buttons and groups when their position is changed.
      *
      * @param {Drupal.ckeditor.ConfigurationModel} model
+     *   The ckeditor configuration model.
      * @param {bool} isDirty
      *   A model attribute that indicates if the changed toolbar configuration
      *   has been stored or not.
@@ -62,6 +64,7 @@
      * Handles the focus event of elements in the active and available toolbars.
      *
      * @param {jQuery.Event} event
+     *   The focus event that was triggered.
      */
     onFocus: function (event) {
       event.stopPropagation();
@@ -171,6 +174,7 @@
      * Provides help information when a button is clicked.
      *
      * @param {jQuery.Event} event
+     *   The click event for the button click.
      */
     announceButtonHelp: function (event) {
       var $link = $(event.currentTarget);
@@ -199,6 +203,7 @@
      * Provides help information when a separator is clicked.
      *
      * @param {jQuery.Event} event
+     *   The click event for the separator click.
      */
     announceSeparatorHelp: function (event) {
       var $link = $(event.currentTarget);
diff --git a/core/modules/ckeditor/js/views/KeyboardView.js b/core/modules/ckeditor/js/views/KeyboardView.js
index ecd088c..a53a132 100644
--- a/core/modules/ckeditor/js/views/KeyboardView.js
+++ b/core/modules/ckeditor/js/views/KeyboardView.js
@@ -1,6 +1,7 @@
 /**
  * @file
- * A Backbone View that provides the aural view of CKEditor keyboard UX configuration.
+ * A Backbone View that provides the aural view of CKEditor keyboard UX
+ *   configuration.
  */
 
 (function (Drupal, Backbone, $) {
@@ -32,6 +33,7 @@
      * Handles keypresses on a CKEditor configuration button.
      *
      * @param {jQuery.Event} event
+     *   The keypress event triggered.
      */
     onPressButton: function (event) {
       var upDownKeys = [
@@ -69,10 +71,11 @@
         var $originalGroup = $group;
         var dir;
 
-        // Move available buttons between their container and the active toolbar.
+        // Move available buttons between their container and the active
+        // toolbar.
         if (containerType === 'source') {
-          // Move the button to the active toolbar configuration when the down or
-          // up keys are pressed.
+          // Move the button to the active toolbar configuration when the down
+          // or up keys are pressed.
           if (_.indexOf([40, 63233], event.keyCode) > -1) {
             // Move the button to the first row, first button group index
             // position.
@@ -142,8 +145,8 @@
         }
         // Move dividers between their container and the active toolbar.
         else if (containerType === 'dividers') {
-          // Move the button to the active toolbar configuration when the down or
-          // up keys are pressed.
+          // Move the button to the active toolbar configuration when the down
+          // or up keys are pressed.
           if (_.indexOf([40, 63233], event.keyCode) > -1) {
             // Move the button to the first row, first button group index
             // position.
@@ -169,8 +172,8 @@
           else {
             view.$el.find('.ui-sortable').sortable('refresh');
           }
-          // Refocus the target button so that the user can continue from a known
-          // place.
+          // Refocus the target button so that the user can continue from a
+          // known place.
           $target.trigger('focus');
         });
 
@@ -183,6 +186,7 @@
      * Handles keypresses on a CKEditor configuration group.
      *
      * @param {jQuery.Event} event
+     *   The keypress event triggered.
      */
     onPressGroup: function (event) {
       var upDownKeys = [
diff --git a/core/modules/ckeditor/js/views/VisualView.js b/core/modules/ckeditor/js/views/VisualView.js
index b9779a2..c165152 100644
--- a/core/modules/ckeditor/js/views/VisualView.js
+++ b/core/modules/ckeditor/js/views/VisualView.js
@@ -34,12 +34,17 @@
     },
 
     /**
+     * Render function for rendering the toolbar configuration.
      *
      * @param {*} model
+     *   Model used for the view.
      * @param {string} [value]
+     *   The value that was changed.
      * @param {object} changedAttributes
+     *   The attributes that was changed.
      *
      * @return {Drupal.ckeditor.VisualView}
+     *   The {@link Drupal.ckeditor.VisualView} object.
      */
     render: function (model, value, changedAttributes) {
       this.insertPlaceholders();
@@ -65,6 +70,7 @@
      * Handles clicks to a button group name.
      *
      * @param {jQuery.Event} event
+     *   The click event on the button group.
      */
     onGroupNameClick: function (event) {
       var $group = $(event.currentTarget).closest('.ckeditor-toolbar-group');
@@ -78,6 +84,7 @@
      * Handles clicks on the button group names toggle button.
      *
      * @param {jQuery.Event} event
+     *   The click event on the toggle button.
      */
     onGroupNamesToggleClick: function (event) {
       this.model.set('groupNamesVisible', !this.model.get('groupNamesVisible'));
@@ -88,6 +95,7 @@
      * Prompts the user to provide a name for a new button group; inserts it.
      *
      * @param {jQuery.Event} event
+     *   The event of the button click.
      */
     onAddGroupButtonClick: function (event) {
 
@@ -120,6 +128,7 @@
      * Handles jQuery Sortable stop sort of a button group.
      *
      * @param {jQuery.Event} event
+     *   The event triggered on the group drag.
      * @param {object} ui
      *   A jQuery.ui.sortable argument that contains information about the
      *   elements involved in the sort action.
@@ -138,6 +147,7 @@
      * Handles jQuery Sortable start sort of a button.
      *
      * @param {jQuery.Event} event
+     *   The event triggered on the group drag.
      * @param {object} ui
      *   A jQuery.ui.sortable argument that contains information about the
      *   elements involved in the sort action.
@@ -153,6 +163,7 @@
      * Handles jQuery Sortable stop sort of a button.
      *
      * @param {jQuery.Event} event
+     *   The event triggered on the button drag.
      * @param {object} ui
      *   A jQuery.ui.sortable argument that contains information about the
      *   elements involved in the sort action.