async / defer wordpress scripts

async-wpscripts

function js_async_attr($tag){
  # Do not add defer or async attribute to these scripts
  $scripts_to_exclude = array('script1.js', 'script2.js', 'script3.js');
  foreach($scripts_to_exclude as $exclude_script){
    if(true == strpos($tag, $exclude_script ) )
    return $tag; 
  }

  # Defer or async all remaining scripts not excluded above
  return str_replace( ' src', ' defer="defer" src', $tag );
}
add_filter( 'script_loader_tag', 'js_async_attr', 10 );