array( string target_domain, string target_type, string semver, string path_prefix ) )`. */ private static $domain_map = array(); /** * Constructor. * * Static-only class, so nothing here. */ private function __construct() {} // //////////////////// // region Async script loading /** * Get the singleton instance of the class. * * @return Assets */ public static function instance() { if ( ! isset( self::$instance ) ) { self::$instance = new Assets(); } return self::$instance; } /** * A public method for adding the async script. * * @deprecated Since 2.1.0, the `strategy` feature should be used instead, with the "defer" setting. * * @param string $script_handle Script handle. */ public static function add_async_script( $script_handle ) { _deprecated_function( __METHOD__, '2.1.0' ); wp_script_add_data( $script_handle, 'strategy', 'defer' ); } /** * Add an async attribute to scripts that can be loaded deferred. * https://developer.mozilla.org/en-US/docs/Web/HTML/Element/script * * @deprecated Since 2.1.0, the `strategy` feature should be used instead. * * @param string $tag The