如何在Joi验证器中基于对象外部的字段进行条件验证

const Joi = require('joi');

const schema = Joi.object({
  type: Joi.string().valid('admin', 'user').required(),
  isAdmin: Joi.boolean(),
  email: Joi.string().email().when('type', {
    is: 'admin',
    then: Joi.required(),
    otherwise: Joi.optional()
  })
});

const data = {
  type: 'admin',
  isAdmin: true,
  email: 'admin@example.com'
};

const result = schema.validate(data);
console.log(result);