loadjs异步加载javascript回调

function loadjs(url,callback){

var script=document.createElement('script');

script.type="text/javascript";

script.src=url;

if(script.onreadystatechange){

script.onreadystatechange=function(){

if(script.readyState='loaded'||script.readyState='complate'){

callback();//script is loaded;

}

}

}else{

script.onloaded=function(){

callback();//script is loaded;

}

}

document.getElementsByTagName('head')[0].appendChild(script);

}

function callback(){

alert("script is loaded");

}

//window.onload之后才去加载的js，这样拆分js的加载有利于首页加载速度提高用户体验

window.onload=function(){

loadjs("jquery.js",callback);

loadjs("test.js",callback);

}