AJAX初级聊天室代码

  var url = "chat.asp?clien="+nowNum+"&cont="+createQueryString("inputs")+named+"&timeStamp="+new Date().getTime();
        xmldoc.open("GET",url,true);
        xmldoc.onreadystatechange = CheckState;
        xmldoc.setRequestHeader("Content-Type","text/xml;charset=GB2312;");
        xmldoc.send(null);
        getId("errors").innerHTML = ""
        addChat(createQueryString("inputs"));
        clean()
        focs()
    }else{
        getId("loadifo").innerHTML = "请输入对话内容！"    
        focs()
    }
}
function CheckState(){
    if(xmldoc.readyState == 1){
        //getId("loadifo").innerHTML = "连接服务器"
        }
    else if(xmldoc.readyState == 2){
        //getId("loadifo").innerHTML = "开始加载数据"
        }
    else if(xmldoc.readyState == 3){
        //getId("loadifo").innerHTML = "正在加载数据"
        }
    else if(xmldoc.readyState == 4){
        if(xmldoc.status == 200){
            results()
        }
        else{
            getId("loadifo").innerHTML = "错误"+xmldoc.status;
            focs()
        }
    }
}
function results(){
    resXml()
}
function resXml(){
    var res = xmldoc.responseXML.documentElement;
    var resLen = res.getElementsByTagName("items").length
    if(getTag(res,0,"num") != nowNum){
        //alert(xmldoc.responseXML.xml)
        nowNum = getTag(res,0,"num")
        for(var i=0; i<resLen; i++){
            var useName = getTag(res,i,"name")
            var useMag = getTag(res,i,"conts")
            var useIp = getTag(res,i,"ip")