ajax的问题，帮忙看段代码！

//用不了啊！
var xmlHttp
//
function showUser()
{
xmlHttp=GetXmlHttpObject()
if (xmlHttp==null)
  {
  alert ("Browser does not support HTTP Request")
  return
  }
var url="lucky.php"
myRand = parseInt(Math.random()*999999999999);
var theURL =url+"?rand="+myRand;
xmlHttp.open("GET","a.php",true)
xmlHttp.onreadystatechange=stateChanged
}
//
function stateChanged()
{
if (xmlHttp.readyState==4&&xmlHttp.status==200){
alert("s");
/* xmlDoc=xmlHttp.responseXml;
var s = xmlDoc.getElementByTagName("tel")[0].nodeValue;*/
}
}
//
function GetXmlHttpObject()
{
var objXMLHttp=null
if (window.XMLHttpRequest)
  {
  objXMLHttp=new XMLHttpRequest()
  }
else if (window.ActiveXObject)
  {
  objXMLHttp=new ActiveXObject("Microsoft.XMLHTTP")
  }
return objXMLHttp
}

用火狐的FIREBUG看看 是否报错

ajax的兼容性是个大问题，给你一个封装好的对象。直接用吧。连方法都封装好了。用aj.post()或者aj.get()直接用即可。重点看看回调函数。依你的智慧，应该没问题的



var aj=new Object();
aj.request=function(){

    if(window.XMLHttpRequest){

        var ajax=new XMLHttpRequest();

    }else{

    var arra=['Microsoft.XMLHTTP', 'MSXML.XMLHTTP', 'Microsoft.XMLHTTP', 'Msxml2.XMLHTTP.7.0', 'Msxml2.XMLHTTP.6.0', 'Msxml2.XMLHTTP.5.0', 'Msxml2.XMLHTTP.4.0', 'MSXML2.XMLHTTP.3.0', 'MSXML2.XMLHTTP'];

    for(i=0;i<arra.length;i++){
        try{
            var ajax=new ActiveXObject(arra);
            if(ajax){
                return ajax;
            }

        }catch(e){
            
            var ajax=false;

        }    


    }

}
        return ajax;    
}
aj.req=aj.request();


aj.Handle=function(callback){
    aj.req.onreadystatechange=function(){

        if(aj.req.readyState==4){
            if(aj.req.status==200){
                callback(aj.req.responseText);
            }

        }

    }

}


aj.cl=function(o){
    if(typeof(o)=='object'){
        var str='';
        for(a in o){
            str+=a+'='+o[a]+'&';

        }
        str=str.substr(-1);
        return str;

    }else{

        return o;
    }

}

aj.get=function(url,callback){

    aj.req.open('get',url);
    aj.req.send(null);

    

    aj.Handle(callback);


}

aj.post=function(url,content,callback){
    aj.req.open('post',url);
    aj.req.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
    content=aj.cl(content);
    aj.req.send(content);
    aj.Handle(callback);
    
}