var el = document.createElement("script"),
loaded = false;
el.onload = el.onreadystatechange = function () {
if ((el.readyState && el.readyState !== "complete" && el.readyState !== "loaded") || loaded) {
return false;
}
el.onload = el.onreadystatechange = null;
loaded = true;
// done!
};
el.async = true;
el.src = path;
var hhead = document.getElementsByTagName('head')[0];
hhead.insertBefore(el, hhead.firstChild);