JS正则表达式验证IP地址

<script type="text/javascript">
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);
}
</script>