function _handleExpandBegin( event ) {
      var menu = event.target;
      _handleToggle( menu );
      if ( menu === _rootMenu ) {
        this.dispatchEvent( 'rootExpandBegin', { target: this } );
        _bodyDom.addEventListener( 'mousedown', _handleBodyClick );
      }

      // TODO: Enable or remove when keyboard navigation is in.
      // If on a submenu, focus the back button, otherwise focus the first link.
      // var firstMenuLink;
      // if ( _activeMenu === _rootMenu ) {
      //   firstMenuLink = _activeMenuDom.querySelector( 'a' );
      // } else {
      //   firstMenuLink = _activeMenuDom.querySelector( 'button' );
      // }
      // firstMenuLink.focus();
    }
/**
     * Event handler for when FlyoutMenu expand transition begins.
     * Use this to perform post-expandBegin actions.
     * @param {Event} event - A FlyoutMenu event.
     */
Event handler for when FlyoutMenu expand transition begins.
Use this to perform post-expandBegin actions.
@param {Event} event - A FlyoutMenu event.
Event handler for when FlyoutMenu expand transition begins . Use this to perform post - expandBegin actions . @param { Event } event - A FlyoutMenu event .
function _handleExpandBegin( event ) {
      var menu = event.target;
      _handleToggle( menu );
      if ( menu === _rootMenu ) {
        this.dispatchEvent( 'rootExpandBegin', { target: this } );
        _bodyDom.addEventListener( 'mousedown', _handleBodyClick );
      }
    }
function _handleExpandBegin ( event ) { var menu = event . target ; _handleToggle ( menu ) ; if ( menu === _rootMenu ) { this . dispatchEvent ( 'rootExpandBegin' , { target : this } ) ; _bodyDom . addEventListener ( 'mousedown' , _handleBodyClick ) ; } }
Event handler for when FlyoutMenu expand transition begins.
Event handler for when FlyoutMenu expand transition begins .
// TODO: Enable or remove when keyboard navigation is in. // If on a submenu, focus the back button, otherwise focus the first link. // var firstMenuLink; // if ( _activeMenu === _rootMenu ) { //   firstMenuLink = _activeMenuDom.querySelector( 'a' ); // } else { //   firstMenuLink = _activeMenuDom.querySelector( 'button' ); // } // firstMenuLink.focus();