动态加载js文件简单示例

function loadScript(url){
var hd = document.getElementsByTagName('head')[0],
js = document.createElement('script');
js.src = url;
js.type = "text/JavaScript";
if(js.addEventListener){
js.addEventListener("load", function(){alert('loaded');}, false);
}else if(js.attachEvent){
js.attachEvent("onreadystatechange", function(){
if(js.readyState === "loaded" || js.readyState === "complete"){
alert('loaded');
}
});
}
hd.appendChild(js);
}