function ajax(url, fnSucc, fnFaild)
{
	//1.创建Ajax对象
	var oAjax=null;
	
	if(window.XMLHttpRequest)
	{
		oAjax=new XMLHttpRequest();
	}
	else
	{
		oAjax=new ActiveXObject("Microsoft.XMLHTTP");
	}
	
	//2.连接服务器
	oAjax.open(‘GET‘, url, true);
	
	//3.发送请求
	oAjax.send();
	
	//4.接收服务器的返回
	oAjax.onreadystatechange=function ()
	{
		if(oAjax.readyState==4)	//完成
		{
			if(oAjax.status==200)	//成功
			{
				fnSucc(oAjax.responseText);
			}
			else
			{
				if(fnFaild)
					fnFaild(oAjax.status);
			}
		}
	};
}
原文:http://www.cnblogs.com/Greenzgz/p/4278117.html