upgrades core to 8.4.2

core/modules/book/book.js

@@ -1,37 +1,25 @@
 /**
- * @file
- * Javascript behaviors for the Book module.
- */
+* DO NOT EDIT THIS FILE.
+* See the following change record for more information,
+* https://www.drupal.org/node/2815083
+* @preserve
+**/
 
 (function ($, Drupal) {
-
-  'use strict';
-
-  /**
-   * Adds summaries to the book outline form.
-   *
-   * @type {Drupal~behavior}
-   *
-   * @prop {Drupal~behaviorAttach} attach
-   *   Attaches summary behavior to book outline forms.
-   */
   Drupal.behaviors.bookDetailsSummaries = {
-    attach: function (context) {
+    attach: function attach(context) {
       $(context).find('.book-outline-form').drupalSetSummary(function (context) {
         var $select = $(context).find('.book-title-select');
         var val = $select.val();
 
         if (val === '0') {
           return Drupal.t('Not in book');
-        }
-        else if (val === 'new') {
+        } else if (val === 'new') {
           return Drupal.t('New book');
         }
-        else {
-          return Drupal.checkPlain($select.find(':selected').text());
-        }
+
+        return Drupal.checkPlain($select.find(':selected').text());
       });
     }
   };
-
-})(jQuery, Drupal);
+})(jQuery, Drupal);