1 - Injecter javascript en asynchrone externe (non bloquant)
<!-- BAD: blocking external script -->
<script src="http://somehost.com/awesome-widget.js"></script>
<!-- GOOD: remote script is loaded asynchronously -->
<script>
var script = document.createElement('script');
script.src = "http://somehost.com/awesome-widget.js";
document.getElementsByTagName('head')[0].appendChild(script);
</script>
<!-- GOOD: modern, simpler, faster, and better all around -->
<script src="http://somehost.com/awesome-widget.js" async></script>