js纯ajax

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);
            }


        }
    }

}