wp register menu query

// menu add query ...........................
add_action('init', 'my_own_custom_menu');

  if(!function_exists('my_own_custom_menu')){
    function my_own_custom_menu(){

      // main menu add query
      register_nav_menu('nav-menu', 'main menu');

      // footer menu add query
      register_nav_menu('footer', 'footer menu');

  }
    }