比较简单的异步加载JS文件的代码

<script> 
function getJsFile(url, callBack){ 
var XH = window.XMLHttpRequest ? new XMLHttpRequest : new ActiveXObject('Msxml2.XMLHTTP'); 
XH.open('get',url,true); 
XH.onreadystatechange = function(){ 
if(XH.readyState == 4 && XH.status == 200){ 
if(window.execScript) window.execScript(XH.responseText); 
else eval.call(window, XH.responseText); 
eval(callBack)(); 
} 
} 
XH.send(''); 
} 
</script>

//test 
<script> 
function cb(){ 
alert(1); 
abc(); //这个是在js9.js 中的 
} 
getJsFile('https://3water.com/images/test.js,'cb'); 
</script>