异步加载

 异步加载

<script type="text/javascript">
    var script = document.createElement('script');
    script.type="text/javascript";
    script.src="demo.js";
    script.onload=function(){
        test();
}
    document.head.appendChild(script)
</script>

script.οnlοad=function(){IE浏览器上没有

当执行onload时文件加载成

}

IE：script.readyState="complete/loaded"

script.onreadystatechange=function(){

        if(script.readyState="complete"||script.readyState="loaded")

}

当满足一定条件才执行的函数叫做回调函数