// Title: Remove query string from static files
// Description: Used to remove the version from the URL of the resources
// of the theme to improve performance and avoid caching issues when updating them.
function remove_cssjs_ver( $src ) {
 if( strpos( $src, '?ver=' ) )
 $src = remove_query_arg( 'ver', $src );
 return $src;
}
add_filter( 'style_loader_src', 'remove_cssjs_ver', 10, 2 );
add_filter( 'script_loader_src', 'remove_cssjs_ver', 10, 2 );

// Title: Defer parsing of JavaScript
// Description: Used to get better performance results by
// defering parsing of all the JavaScript files inside the header.
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 );