function ajax(){}

ajax.getXmlHttpObj = function()
{
	if(typeof XMLHttpRequest != "undefined")
	{
		return new XMLHttpRequest();
	}
	else if(window.ActiveXObject)
	{
		var aVersion =["MSXML2.XMLHttp.5.0",
						"MSXML2.XMLHttp.4.0",
						"MSXML2.XMLHttp.3.0",
						"MSXML2.XMLHttp",
						"Microsoft.XMLHttp"];
		for(var i=0;i<aVersion.length;i++)
		{
			try
			{
				var oXmlHttp = new ActiveXObject(aVersion[i]);
				return oXmlHttp;
			}
			catch(e)
			{
				
			}
		}
	}
	throw new Error("XMLHttp object can't be create!");
};



//通过同步POST方式获得指定服务端的数据
//url 指定的服务端处理文件路径
//post 发送的数据
ajax.postText = function(url,postData)
{
    var xmlhttp = this.getXmlHttpObj();
    xmlhttp.open("POST", url, false);
    xmlhttp.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
    xmlhttp.send(postData);
	if(xmlhttp.readyState == 4 && xmlhttp.status == 200)
	{
		return xmlhttp.responseText;
	}
	else
	{
	    return null;
	}
};