public function headerDeferJavascripts()
    {
        add_filter('script_loader_tag', function ($tag, $handle) {
            // Main WP jQuery is not concerned
            if (strpos($tag, '/wp-includes/js/jquery/jquery')) {
                return $tag;
            }

            // Defer on MSIE is not permitted
            if (isset($_SERVER['HTTP_USER_AGENT']) && false !== strpos($_SERVER['HTTP_USER_AGENT'], 'MSIE 9.')) {
                return $tag;
            }

            return str_replace(' src', ' defer src', $tag);
        }, 10, 2);
    }