3.3 Joi JavaScript对象的规则描述语言和验证器。 `npm install joi` ~~~ const Joi = require('joi') ; const schema ={ username: Joi. string() . alphanum() .min(3) .max(30) . required() .error (new Error(错误信息' )， password: Joi . string() . regex(/^[a-zA-Z0-9] {3,30}$/)， access_token: [Joi.string() ，Joi . number()]， birthyear: Joi . number() . integer() .min(1900) .max(2013) , email: Joi.string() .email () }; ~~~