Source: modules/toolbar/js/models/MenuModel.es6.js

/**
 * @file
 * A Backbone Model for collapsible menus.
 */

(function (Backbone, Drupal) {
  /**
   * Backbone Model for collapsible menus.
   *
   * @constructor
   *
   * @augments Backbone.Model
   */
  Drupal.toolbar.MenuModel = Backbone.Model.extend(
    /** @lends Drupal.toolbar.MenuModel# */ {
      /**
       * @type {object}
       *
       * @prop {object} subtrees
       */
      defaults: /** @lends Drupal.toolbar.MenuModel# */ {
        /**
         * @type {object}
         */
        subtrees: {},
      },
    },
  );
})(Backbone, Drupal);