var request=null;
if(window.XMLHttpRequest){
	try{
		request=new XMLHttpRequest();
	}catch(e){
		request=null;
	}
}else if(window.ActiveXObject){
	try{
		request=new ActiveXObject("Msxm12.XMLHTTP");
	}catch(e){
		try{
			request=new ActiveXObject("Microsoft.XMLHTTP");
		}catch(e){
			request=null;
		}
	}
}

AjaxRequest.prototype.send=function(type,url,handler,postDataType,postData){
	if(this.request!=null){
		//kill the previous request
		this.request.abort();
		
		try{
			this.request.onreadystatechange=handler;   //自定义的处理器函数
			this.request.open(type,url,true);
			if(type.toLowerCase()=="get"){     //发送get请求
				this.request.send(null);
			}else{                      //发送post请求
				this.request.setRequestHeader("Content-Type",postDataType);
				this.request.send(postData);
			}
		}catch(e){
			alert("Ajax error communicating with the server.\n"+"Details:"+e);
		}
	}
}

var ajaxReq=new AjaxRequest();
ajaxReq.send("GET","movies.xml",handleRequest);