joi.js

const Joi = require('joi')

const ukzip = /^[A-Z]{1,2}[0-9]{1,2}[A-Z]{0,1} ?[0-9][A-Z]{2}$/i

module.exports = Joi.extend({
  name: 'number',
  base: Joi.number().strict()
}, {
  name: 'zipcode',
  base: Joi.regex(ukzip).description('UK Zipcode')
})