WordPress Version: 5.9
/**
* Retrieves all registered navigation menu locations and the menus assigned to them.
*
* @since 3.0.0
*
* @return int[] Associative array of registered navigation menu IDs keyed by their
* location name. If none are registered, an empty array.
*/
function get_nav_menu_locations()
{
$locations = get_theme_mod('nav_menu_locations');
return is_array($locations) ? $locations : array();
}