常见正则表达式
1 用户名 /^[a-z0-9_-]{3,16}$/ 2 密码 /^[a-z0-9_-]{6,18}$/ 3 十六进制值 /^#?([a-f0-9]{6}|[a-f0-9]{3})$/ 4 电子邮箱 /^([a-z0-9_\.-]+)@([\da-z\.-]+)\.([a-z\.]{2,6})$/ 5 /^[a-z\d]+(\.[a-z\d]+)*@([\da-z](-[\da-z])?)+(\.{1,2}[a-z]+)+$/ 6 URL /^(https?:\/\/)?([\da-z\.-]+)\.([a-z\.]{2,6})([\/\w \.-]*)*\/?$/ 7 IP 地址 /((2[0-4]\d|25[0-5]|[01]?\d\d?)\.){3}(2[0-4]\d|25[0-5]|[01]?\d\d?)//^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$/
