JS正则表达式验证IP地址

	var ip="255.255.255.255";
	alert(isIP(ip));
	alert(isIP2(ip));
	function isIP(ip)
	{
		var reSpaceCheck = /^(\d+)\.(\d+)\.(\d+)\.(\d+)$/;
		if (reSpaceCheck.test(ip))
		{
			ip.match(reSpaceCheck);
			if (RegExp.$1<=255&&RegExp.$1>=0
			  &&RegExp.$2<=255&&RegExp.$2>=0
			  &&RegExp.$3<=255&&RegExp.$3>=0
			  &&RegExp.$4<=255&&RegExp.$4>=0)
			{
				return true; 
			}else
			{
				return false;
			}
		}else
		{
			return false;
		}
	}
	function isIP2(ip) 
	{ 
		var re =  /^(\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\.(\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\.(\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\.(\d{1,2}|1\d\d|2[0-4]\d|25[0-5])$/ 
		return re.test(ip); 
	}