原生写法

    var ajax = new XMLHttpRequest();
    ajax.open("get",url?data);
    ajax.setRequestHeader("Content-type","application/x-www-form-urlencoded");
    ajax.send(data);
    ajax.onreadystatechange = function(){
        if(ajax.readyState === 4 && ajax.status === 200){
            console.log(ajax.responseText);
        }
    }