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  $menu_name = 'mobile-menu';
  $locations = get_nav_menu_locations();
  $menu = wp_get_nav_menu_object( $locations[ $menu_name ] );
  $menuitems = wp_get_nav_menu_items( $menu->term_id, array( 'order' => 'DESC' ) );

//echo '<pre>'.print_r($menuitems).'</pre>';

function buildTree( array &$elements, $parentId = 0 )
{
    $branch = array();
    foreach ( $elements as &$element )
    {
        if ( $element->menu_item_parent == $parentId )
        {
            $children = buildTree( $elements, $element->ID );
            if ( $children )
                $element->wpse_children = $children;

            $branch[$element->ID] = $element;
            unset( $element );
        }
    }
    return $branch;
}
$menuitems = buildTree($menuitems);