ajax 的 xmlhttp request对象的 面向对象封装

在做这个网站的时候， 有些地方要用到简单的ajax效果。用框架也太不麻烦了，所以索性自己封装了一个简洁的ajax的类，当然也和大家分享一下：

//ajax.js代码start

function xmlhttpcls(url, verb)
{
   var request = get_xmlhttp_obj();  
   this.callback = null;
   var params = [];
   //
  this.add = function (pname, pvalue)
  {
    params[params.length] = new param(pname, pvalue);
  }  
   //
   this.getText = function()
   {
        return request.responseText;
   }
   //
   this.getXml = function()
   {
        return request.responseXML;
   }
   //
   this.send = function()
   { 
       var callback =  this.callback;
       request.onreadystatechange = function()
       {
            if (request.readyState == 4)
            {               
                if(request.status == 200)
                    callback();
                else
                {
                    document.write("ERR[" + request.status + "] : " + request.statusText
                        + "<br>" + url + "<br>" + getUrlParamString(params));
                }
            }
       };
      
       if (verb != null && verb == "post")
       {           
            request.open("POST",url,true);
            request.setRequestHeader("Content-Type","application/x-www-form-urlencoded");
            request.setRequestHeader("If-Modified-Since","0");
            request.send(getUrlParamString(params));
       }
       else
       {
            var urlparams = getUrlParamString(params);
            if (urlparams != null)
            {
                 urlparams = "?" + urlparams;
            }
            request.open("GET",url + urlparams,true);
            request.setRequestHeader("If-Modified-Since","0");
            request.send(null);
       }
   }
  //
  var getUrlParamString = function(ps)
  {
        var urlString = null;
        if (ps.length > 0)
        {
             urlString = "";
             for (var i = 0 ; i < ps.length; i++)
             {
                  urlString = urlString + (i == 0 ? "" : "&");
                  urlString += ps[i].name + "=" + ps[i].value;
             }
        }
        return urlString;
  }
  //
}

function param(pname, pvalue)
{
    this.name = pname;
    this.value = pvalue;
}

function get_xmlhttp_obj()
{
    var http_request = null;
    if(window.XMLHttpRequest) //其他浏览器 Mozilla,
 {
  http_request=new XMLHttpRequest();
  if(http_request.overrideMimeType)
  {
   http_request.overrideMimeType("text/xml");
  }
 }
 else if(window.ActiveXObject) //IE
 {
  try
  {
   http_request=new ActiveXObject("Msxml2.XMLHTTP");

  }
  catch(e)
  {
   try
   {
    http_request=new ActiveXObject("Microsoft.XMLHTTP");
   }
   catch(e){}
  }
 }
 return http_request;
}

//ajax.js代码end

下面是HTML页面中的调用代码

var xmlhttp = new xmlhttpcls("请求的url", "post");  // 若第二个参数不填或者写"get"则为get方式
xmlhttp.add("参数1", "参数1的值");
xmlhttp.add("参数2", "参数1的值"); 
xmlhttp.callback = function()
{
       var temptext = xmlhttp.getText();
       var tempXmlDOM = xmlhttp.getXml();
}
xmlhttp.send();

是不是很有点简单 。