WordPress defer javascript filter

simple-map-defer.php

/**
 * defer javascript!
 * 
 */
function defer_parsing_of_js($url)
{
  if (FALSE === strpos($url, '.js')) return $url;
  if (strpos($url, 'jquery.js')) return $url;
  return "$url' defer ";
}
add_filter('clean_url', 'defer_parsing_of_js', 11, 1);