js原生 Ajax

 1  //1.new一个XMLHttpRequest 兼容性写法
 2 var xmlhttp;
 3     if (window.XMLHttpRequest) {
 4         xmlhttp = new XMLHttpRequest();
 5     } else {
 6         xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
 7     }
 8     //2.定义请求方式
 9     xmlhttp.open("GET", "http://yapi.shangyuninfo.com/mock/156/bookType")
10     //3.向服务器发送请求
11     xmlhttp.send();
12     //4.响应与数据处理
13     xmlhttp.onreadystatechange = function (res) {
14         if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
15             console.log(res.currentTarget.response);
16             var resout = JSON.parse(res.currentTarget.response)
17             console.log(resout.book[0].typeList);
18         }
19     }
20