$handle ) { if ( ! array_key_exists( $handle, $wp_scripts->registered ) ) { continue; } $polyfill .= ( // Test presence of feature... '( ' . $test . ' ) || ' . // ...appending polyfill on any failures. Cautious viewers may balk // at the `document.write`. Its caveat of synchronous mid-stream // blocking write is exactly the behavior we need though. 'document.write( \'