function ajax(url,fnWin,fnFaild){
    //1.创建ajax对象
    var xhr = window.XMLHttpRequest ? new XMLHttpRequest() : new ActiveXObject("Microsoft.XMLHTTP");
    //2.与服务器建立连接
    xhr.open("GET",url,true);
    //3.发送请求
    xhr.send();
    //4.接收服务器返回的信息
    xhr.onreadystatechange = function(){
        if(xhr.readyState == 4){
            if(xhr.status == 200){
                fnWin && fnWin(xhr.responseText);
            }else{
                fnFaild && fnFaild();
            }
        }
    }
}