Issue #2504713 by eiriksm, nod_, jhodgdon: JSDoc book module

core/modules/book/book.js

@@ -8,7 +8,12 @@
   "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) {