AJAX request queue implementation

//Ajax Function
var reqObj; //Creat Null Instence
var RequestArray = new Array();
//var whichRequest;
//加入请求队列
function AddRequestArray(url,isAsy,method,parStr,callBackFun)
{
    var ArgItem = new Array();
    ArgItem[0]=url;
    ArgItem[1]=isAsy;
    ArgItem[2]=method;
    ArgItem[3]=parStr;
    ArgItem[4]=callBackFun;
    RequestArray.push(ArgItem);   //将当前请求添加到队列末尾
    if(RequestArray.length==1) //如果请求队列里只有当前请求立即要求执行队列，如果有其他请求，那么就不要求执行队列
    {
      ExeRequestArray();
    }
}

//执行队列里的顺序第一个的请求
function ExeRequestArray()
{
  if( RequestArray.length>0) //如果队列里有请求执行 AJAX请求
  {
    var ArgItem = RequestArray[0];  DoRequest(ArgItem[0],ArgItem[1],ArgItem[2],ArgItem[3],ArgItem[4]);
  }
}
//Run Ajax (string urladdress,bool IsAsy,string method,string parameters,string whichRequest)
function DoRequest(url,isAsy,method,parStr,callBackFun) 
{
  reqObj = false;
  //whichRequest = whichReq;
  if (window.XMLHttpRequest) //compatible Mozilla, Safari,...
  {
    reqObj = new XMLHttpRequest();       //Creat XMLHttpRequest Instance
    if (reqObj.overrideMimeType)        //if Mime Type is false ,then set MimeType 'text/xml'
    {
      reqObj.overrideMimeType('text/xml');
    }
  }
  else if (window.ActiveXObject) //compatible IE
  {
    try
    {
      reqObj = new ActiveXObject("Msxml2.XMLHTTP"); //Creat XMLHttpRequest Instance
    }
    catch (e)
    {
      try
      {
        reqObj = new ActiveXObject("Microsoft.XMLHTTP"); //Creat XMLHttpRequest Instance
      }
      catch (e)
      {}
    }
  }

  //if reqObj is false,then alert warnning
  if (!reqObj)
  {
    alert('Giving up :( Cannot create an XMLHTTP instance');
    return false;

  }
  reqObj.onreadystatechange = function(){GetRequest(callBackFun)}; //set onreadystatechange Function
  reqObj.open(method, url, isAsy);    //set open Function
  reqObj.setRequestHeader('Content-Type','application/x-www-form-urlencoded'); //set RequestHeader
  reqObj.send(parStr);  //do send and send parameters 
}

//get Service Response information Function
function GetRequest(callBackFun)
{
  //judge readystate information
  if (reqObj.readyState == 4)
  {
    //judge status information
    if (reqObj.status == 200)
    {
      eval(callBackFun+"(reqObj)");
    }
    else
    {
      alert('There was a problem with the request.'+reqObj.status+"CallFunction:"+callBackFun); //else alert warnning
    }
    RequestArray.shift(); //移除队列里的顺序第一个的请求，即当前已经执行完成的请求
    ExeRequestArray();   //要求执行队列中的请求
  }
}