Async Script Loading in Browser Javascript Snippet

load.js

(function(url) {
    var scriptTag = document.createElement('script');
    scriptTag.type = 'text/javascript';
    scriptTag.async = true;
    scriptTag.src = url;
    var s = document.getElementsByTagName('script')[0];
    s.parentNode.insertBefore(scriptTag, s);
})(URL);