CSS delivery optimization: How to defer css loading?

Question

I am trying to optimize the CSS delivery following the google documentation for developers https://developers.google.com/speed/docs/insights/OptimizeCSSDeli

Answer 1

A little modification to the function provided by Fred to make it more efficient and free of jQuery. I am using this function in production for my websites

        // to defer the loading of stylesheets
        // just add it right before the  tag
        // and before any javaScript file inclusion (for performance)  
        function loadStyleSheet(src){
            if (document.createStyleSheet) document.createStyleSheet(src);
            else {
                var stylesheet = document.createElement('link');
                stylesheet.href = src;
                stylesheet.rel = 'stylesheet';
                stylesheet.type = 'text/css';
                document.getElementsByTagName('head')[0].appendChild(stylesheet);
            }
        }