Async Javascript Load

async.html

<!-- Sync script will block rendering of page -->
<script type="text/javascript" src="http://link-to-js-assets.js"></script>

<!-- Async script will not block rendering = Preferred Method -->
<script type="text/javascript">
  (function() {
    var po = document.createElement('script'); po.type = 'text/javascript';
    po.async = true; po.src = 'http://link-to-js-assets.js';
    var s = document.getElementsByTagName('script')[0];
    s.parentNode.insertBefore(po, s);
    })();
</script>