Ajax 的一段代码

function Ajax(url,obj)
{
var request=null;
if( window.XMLHttpRequest ) { request=new XMLHttpRequest(); }
else if( window.ActiveXObject ){ request=new ActiveXObject("Microsoft.XMLHttp"); }
if(request){
request.open("GET", url , true);
request.onreadystatechange = function(){
if(request.readyState==4 && request.status==200)
{
obj.innerHTML =request.responseText;
}else{
obj.innerHTML ="数据加载中";
}
}
request.send(null);
}
}
new Ajax('a.htm', document.getElementById('test'));