var http_request = false;

function createXMLHttpRequest()
{
	http_request = false;
		
	//开始初始化XMLHttpRequest对象
	if(window.XMLHttpRequest) 
	{ 
		//Mozilla 浏览器
	  http_request = new XMLHttpRequest();
	  if (http_request.overrideMimeType) 
	  {
	  	//设置MiME类别
	    http_request.overrideMimeType("text/xml");
		}
	}
	else if (window.ActiveXObject) 
	{ 
		// IE浏览器
		try 
		{
			http_request = new ActiveXObject("Msxml2.XMLHTTP");
		} 
		catch (e) 
		{
			try 
			{
				http_request = new ActiveXObject("Microsoft.XMLHTTP");
			} 
			catch (e) 
			{}
		}
	}
	
	if (!http_request) 
	{ 
		// 异常，创建对象实例失败
		window.alert("不能创建XMLHttpRequest对象实例.");
	  //return false;
	}	
}

/*
 * 检查用户名是否存在
 */
function checkAcct(url) 
{
		createXMLHttpRequest();
		
		//指定处理函数、发送请求的函数
	 	http_request.onreadystatechange = function()
	 	{
			if (http_request.readyState == 4) 
			{ 
				// 判断对象状态
				if (http_request.status == 200) 
				{ 
					// 信息已经成功返回，开始处理信息
					document.getElementById("checkResult").innerHTML = http_request.responseText;
				} 
		    else if (http_request.status == 404)
		    {
					alert(http_request.responseText);
				}
				else 
				{ 
					//页面不正常
		      alert("您所请求的页面有异常。");
				}
			} 			
	 	}
		// 确定发送请求的方式和URL以及是否同步执行下段代码
		http_request.open("GET", url, true);
		http_request.send(null);
}

/*
 * 首页top登录状态
 */
function loginStat(url) 
{
		createXMLHttpRequest();
		
		//指定处理函数、发送请求的函数
	 	http_request.onreadystatechange = function()
	 	{
			if (http_request.readyState == 4) 
			{ 
				// 判断对象状态
				if (http_request.status == 200) 
				{ 
					// 信息已经成功返回，开始处理信息
					//document.getElementById("loginStat").innerHTML = http_request.responseText;
					if (http_request.responseText == "true")
					{
						var ids = document.getElementsByName("loginStat");
						for (var i=0; i<ids.length; i++)
						{
							if (ids[i].attr) 
							{
								ids[i].style.display = "none";
							}
							else
							{
								ids[i].style.display = "";
							}
						}
					}
					else
					{
						var ids = document.getElementsByName("loginStat");
						for (var i=0; i<ids.length; i++)
						{
							if (ids[i].attr) 
							{
								ids[i].style.display = "";
							}
							else
							{
								ids[i].style.display = "none";
							}
						}
					}
				} 
		        else if (http_request.status == 404)
		        {
					alert(http_request.responseText);
				}
				else 
				{ 
					//页面不正常
		            alert("您所请求的页面有异常。");
				}
			} 			
	 	}
		// 确定发送请求的方式和URL以及是否同步执行下段代码
		http_request.open("GET", url, true);
		http_request.send(null);
}