CSS delivery optimization: How to defer css loading?

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

As you can see in the example of inlining a small CSS file the critical CSS in inlined in the head and the original small.css is loaded after onload of the page.

<html>
  <head>
    <style>
      .blue{color:blue;}
    </style>
    </head>
  <body>
    <div class="blue">
      Hello, world!
    </div>
  </body>
</html>
<noscript><link rel="stylesheet" href="small.css"></noscript>

My question regarding this example:

How to load a large css file after onload of the page?

If you don't mind using jQuery, here is a simple code snippet to help you out. (Otherwise comment and I'll write a pure-js example

function loadStyleSheet(src) {
    if (document.createStyleSheet){
        document.createStyleSheet(src);
    }
    else {
        $("head").append($("<link rel='stylesheet' href='"+src+" />"));
    }
};

Just call this in your $(document).ready() or window.onload function and you're good to go.

For #2, why don't you try it out? Disable Javascript in your browser and see!

By the way, it's amazing how far a simple google search can get you; for the query "post load css", this was the fourth hit... http://www.vidalquevedo.com/how-to-load-css-stylesheets-dynamically-with-jquery

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 </body> 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);
            }
        }

This is how you do it using the new way:

<link rel="preload" href="styles.css" as="style" onload="this.onload=null;this.rel='stylesheet'">
<noscript><link rel="stylesheet" href="styles.css"></noscript>

link rel="preload" as="style" requests the stylesheet asynchronously.
The onload attribute in the link allows the CSS to be processed when it finishes loading.
"nulling" the onload handler once it is used helps some browsers avoid re-calling the handler upon switching the rel attribute.
The reference to the stylesheet inside of a noscript element works as a fallback for browsers that don't execute JavaScript.

In addition to Fred's answer:

Solution using jQuery & Noscript

<html>
  <head>
    <style>
      .blue{color:blue;}
    </style>
    <script type="text/javascript" src="../jquery-1.4.2.min.js"></script>
    <script type="text/javascript">
        $(document).ready(function(){
        if($("body").size()>0){
                if (document.createStyleSheet){
                    document.createStyleSheet('style.css');
                }
                else {
                    $("head").append($("<link rel='stylesheet' 
                    href='style.css' 
                    type='text/css' media='screen' />"));
                }
            }
        });
    </script>
    </head>
  <body>
    <div class="blue">
      Hello, world!
    </div>
  </body>
</html>
<noscript><link rel="stylesheet" href="small.css"></noscript>

from http://www.vidalquevedo.com/how-to-load-css-stylesheets-dynamically-with-jquery

Using pure Javascript & Noscript

<html>
  <head>
    <style>
      .blue{color:blue;}
    </style>
    <script type="text/javascript">
          var stylesheet = document.createElement('link');
          stylesheet.href = 'style.css';
          stylesheet.rel = 'stylesheet';
          stylesheet.type = 'text/css';
          document.getElementsByTagName('head')[0].appendChild(stylesheet);
    </script>
    </head>
  <body>
    <div class="blue">
      Hello, world!
    </div>
  </body>
</html>
<noscript><link rel="stylesheet" href="small.css"></noscript>

Try this snippet

The author claims it was published by Google's PageSpeed Team

<script>
    var cb = function() {
    var l = document.createElement('link'); l.rel = 'stylesheet';
    l.href = 'yourCSSfile.css';
    var h = document.getElementsByTagName('head')[0]; h.parentNode.insertBefore(l, h); };
    var raf = requestAnimationFrame || mozRequestAnimationFrame ||
              webkitRequestAnimationFrame || msRequestAnimationFrame;
    if (raf) raf(cb);
    else window.addEventListener('load', cb);
</script>

CSS delivery optimization: How to defer css loading?

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