JavaScript AJAX原生写法

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<html lang="zh">

    <head>
        <meta charset="UTF-8" />
        <meta name="viewport" content="width=device-width, initial-scale=1.0" />
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        <title>JavaScript AJAX原生写法 面试题</title>
    </head>

    <body>
        <script type="text/javascript">
            var Ajax = {
                get: function(url, fn) {
                    //创建XMLHttpRequest对象
                    var xhr = new XMLHttpRequest();
                    //true表示异步
                    xhr.open('GET', url, true);
                    xhr.onreadystatechange = function() {
                        // readyState == 4说明请求已完成
                        if(xhr.readyState == 4 && xhr.status == 200 || xhr.status == 304) {
                            //responseText：从服务器获得数据
                            fn.call(this, xhr.responseText);
                        }
                    };
                    xhr.send();
                },
                post: function(url, data, fn) { //datat应为'a=a1&b=b1'这种字符串格式
                    var xhr = new XMLHttpRequest();
                    xhr.open("POST", url, true);
                    // 添加http头，发送信息至服务器时内容编码类型
                    xhr.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
                    xhr.onreadystatechange = function() {
                        if(xhr.readyState == 4 && (xhr.status == 200 || xhr.status == 304)) {
                            fn.call(this, xhr.responseText);
                        }
                    };
                    xhr.send(data);
                }
            }
        </script>
    </body>

</html>