搭建Ajax开发框架：

1）编写自定义的javascript函数createrequest()，首先初始化XMLHttpRequest对象，然后指定处理函数，最后发送HTTP请求

代码如下：

<script language="javascript">
    var http_request = false;
    function createRequest(url) {
        http_request = false;
        if (window.XMLHttpRequest) {     // Mozilla浏览器
            http_request = new XMLHttpRequest();
            if (http_request.overrideMimeType) {
                http_request.overrideMimeType('text/xml');     //设置MIME类别
            }
        } else if (window.ActiveXObject) {     // IE浏览器
            try {
                http_request = new ActiveXObject("Msxml2.XMLHTTP");
            } catch (e) {
                try {
                    http_request = new ActiveXObject("Microsoft.XMLHTTP");
               } catch (e) {}
            }
        }
        if (!http_request) {
            alert("不能创建XMLHttpRequest对象实例！");
            return false;
        }
        http_request.onreadystatechange = getResult;     //调用返回结果处理函数
        http_request.open('POST',url,true);
        http_request.send();

    }

/返回结果处理函数
    function getResult() {
        if (http_request.readyState == 4) {     // 判断请求状态
            if (http_request.status == 200) {     // 请求成功，开始处理返回结果
                alert(http_request.responseText);
            } else {     //请求页面有错误
                alert("您所请求的页面有错误！");
            }
        }
    }

<a href="#" onClick="createRequest('goal.htm')">获取请求</a> </body>