Javascript Ajax 请求

    var XMLHttpReq;
    function createXMLHttpRequest() {
        try {
            XMLHttpReq = new ActiveXObject("Msxml2.XMLHTTP");//IE高版本创建XMLHTTP
        }
        catch(E) {
            try {
                XMLHttpReq = new ActiveXObject("Microsoft.XMLHTTP");//IE低版本创建XMLHTTP
            }
            catch(E) {
                XMLHttpReq = new XMLHttpRequest();//兼容非IE浏览器，直接创建XMLHTTP对象
            }
        }  

    }
    function sendAjaxRequest(url) {
        createXMLHttpRequest();                                //创建XMLHttpRequest对象
        XMLHttpReq.open("post", url, true);
        XMLHttpReq.onreadystatechange = processResponse; //指定响应函数
        XMLHttpReq.send(null);
    }
    //回调函数
    function processResponse() {
        if (XMLHttpReq.readyState == 4) {
            if (XMLHttpReq.status == 200) {
                var text = XMLHttpReq.responseText;  

                /**
                 *实现回调
                 */
                text = window.decodeURI(text);
                var cp = document.getElementById("cp");
                cp.innerHTML = "";
                var values = text.split("|");
                for (var i = 0; i < values.length; i++) {
                    var temp = document.createElement("option");
                    temp.text = values[i];
                    temp.value = values[i];
                    cp.options.add(temp);
                }  

            }
        }  

    }