ajax原生态请求写法

<script type="text/javascript">
     var xhr;
     function createXMLHttpReuqest(){
         //创建浏览器
if(window.ActiveXObject){
return new ActiveXObject("Microsoft.XMLHTTP");

}
else if(window.XMLHttpRequest){
return new XMLHttpRequest();

}
         }
function checkLogin() {
// alert("ok");
var url="login.do?name=admin&&password=123";//请求URL
xhr=createXMLHttpReuqest();
xhr.onreadystatechange=okCallMe;
     xhr.open("POST",url,true);
xhr.send(null);

}
function okCallMe(){
//判断处理状态是否为接收结果   状态码是否为200
if(xhr.readystate==4&&xhr.status==200){
         var result=xhr.responseText;
         alert(result);
}

}
</script>