如何给Ajax的回调函数传参数？

如何给Ajax的回调函数传参数？
 1 function GetNewWFLineIDs(count,newLineIds)
 2     {
 3          var url = '../servlet/net.blogjava.lzqdiy.TestAjax';
 4          var cmd='cmd=GetNewWFLineID';
 5          var param='param=<Params><IDCount>'+count+'</IDCount></Params>';
 6 　　     getReqObject();
 7         if(req)
 8         {
 9
10             req.open("POST",url, false);
11             req.onreadystatechange=function(){saveLineIDs(newLineIds);}//给回调函数传参数
12             req.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
13             req.setrequestheader("cache-control","no-cache");
14             var param1=encodeURI(cmd+"&"+param);
15             var param2=encodeURI(param1);
16             req.send(param2);
17 　　     }
18     }回调函数如下:
function saveLineIDs(newLineIds)
    {
        if (req.readyState == 4)
        {
　　         if (req.status == 200)
            { 　            
                var res=req.responseXML;
                var ids=res.getElementsByTagName("WFLineID");
　　            
                for(var i=0;i<ids.length;i++)
                {
　　                 if(isIE)
                    {
                        newLineIds.push(ids[i].childNodes[0].data);
                    }
                    if(isFirefox)
                    {
                        newLineIds.push(ids[i].childNodes[0].nodeValue);
                    }
　　             }
　　         }
　　     }
    }