Ajax封装

var req;
function createXMLHttpRequest(){//创建XMLHttpRequest对象
 var
request; 
 if(window.XMLHttpRequest){
  request=new
XMLHttpRequest();
 }else if(window.ActiveXObject){
   request=new
ActiveXObject("Msxml2.XMLHTTP");
 }
  return request;
}
function
test(method,url,param,Asyhc,handle200,handle404,handle500,locading){
 var
req=createXMLHttpRequest();//创建XMLHttpRequest对象
 req.onreadystatechange=function(){//处理返回数据
  if(4==req.readyState){//服务器已经成功接收数据
   if(200==req.status){//成功返回数据
    handle200(req);//一个函数也是一个对象
   }else
if(404==req.status){
    handle404(req);
   }else
if(500==req.status){
    handle500(req);
   }
  }else{
   locading(req);
  }
 }
 if("get".equals(method.toLowerCase)){//判断是get还是post方法
  req.open("get",url+(param==null?"":"?"+param),Asyhc);
  req.send(null);
 }else
if("post".equals(method.toLowerCase)){
  req.open("post",url,Asyhc);
  req.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
  req.send(param);
 }
}