function newXMLHTMLRequest()
{
    var xmlreq;
    //判断是否支持new XMLHttpRequest创建，如果支持，即非IE浏览器
    if(window.XMLHttpRequest)
    {
        xmlreq = new XMLHttpRequest();
    }
    else
    {
        try
        {
            //IE5.5及以上版本
            xmlreq = new ActiveXObject("Msxml2.XMLHTTP");
        }
        catch(e)
        {
            //IE5及以下版本
            xmlreq = new ActiveXObject("Microsoft.XMLHTTP");
        }
    }
    return xmlreq;
}

function backFun(req,id,isvalue)
{
//返回一个无参的函数
    return function ()
    {
        if(req.readyState == 4 && req.status == 200)
        {
            var contrl = document.getElementById(id);
            if(isvalue)
            {
                contrl.value = req.responseText;
            }
            else
            {
                contrl.innerHTML = req.responseText;
            }
        }
        
    }
}

function talktoServer(id,url,isvalue)
{
    var req = newXMLHTMLRequest();
    var cbf = backFun(req,id,isvalue);
    req.onreadystatechange = cbf;
    req.open("GET",url,true);
    //req.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
    req.send(null);

}