/*
 * Copyright (C) MyCourse Online Education Technology Co., Ltd. All rights reserved.
 * Author: Xuke
 * Created on 2006-11-01
 * Description: AJAX
 * $Heade$
 */

var Ajax = new function()
{
  this.request = function(url, callback, param)
  {
    var ajax;
    if (window.XMLHttpRequest)
      ajax = new XMLHttpRequest();
    else if (window.ActiveXObject)
      ajax = new ActiveXObject("Microsoft.XMLHTTP");
    ajax.open("GET", url, true);
	  ajax.setRequestHeader("If-Modified-Since", 0);
    ajax.send("");
    ajax.onreadystatechange = function ()
    {
      if (ajax.readyState == 4)
        if (ajax.status == 200 || ajax.status == 304)
          if (param != null)
            callback(ajax, param);
          else
            callback(ajax);
    }
  }
}