var reg = /^(([1-9])|([1-9][0-9])|(1[0-9][0-9])|(2[0-4][0-9])|(25[0-5]))\.(([0-9])|([1-9][0-9])|(1[0-9][0-9])|(2[0-4][0-9])|(25[0-5]))\.(([0-9])|([1-9][0-9])|(1[0-9][0-9])|(2[0-4][0-9])|(25[0-5]))\.(([0-9])|([1-9][0-9])|(1[0-9][0-9])|(2[0-4][0-9])|(25[0-5]))$/;var ip = "192.168.30.254";var flag = ip.match(reg) == null ? false : true;alert(flag);