判断IP的正则表达式

 var reg = /^(\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])$/;
            if (!reg.test(RestrictIp)) {
                $("#RestrictIp").focus();
                alert("请输入正确的IP地址！");
                return false;
            }