How to access wordpress menu & submenu item through the REST API?

I want to display the menu submenu items from Wordpress in another web-application, menu and Submenu are get but there is more menu inside Submenu I want that.

function return_menus( $data ) {
$menuID = $data['id']; 
//$primaryNav = wp_get_nav_menu_items($menuID);
$x = wp_get_nav_menu_items($menuID);
// echo 'pre';
//   print_r($x);
// echo '/pre';
    $menu = array();
    $submenu = array();
    foreach($x as $y){
        $y- submenu = array();
        if($y-menu_item_parent === '0')
            array_push($menu, $y);
        else 
            array_push($submenu, $y);
    }
    for($i=0; $i  count($submenu); $i++) {
        $index = get_index($menu,$submenu[$i]-menu_item_parent);
        if($index  -1) {
            array_push($menu[$index]-submenu,$submenu[$i]);
        }
    }
return $menu;
}
function get_index($menu,$parent_id){
    $index = -1;
for($i = 0; $i  count($menu); $i++) {
        if((string)$menu[$i]-ID === $parent_id) {
            $index = $i;
            break;
        }
    }
    return $index;
}
add_action( 'rest_api_init', function () {
    register_rest_route( 'rix', '/menu/(?Pid\d+)', array(
        'methods' = 'GET',
        'callback' = 'return_menus',
    ) );
} );