joi prob

joi-probs.js

const Joi = require('joi');

const payload = [{
  type: 'book',
  author: 'Herman Melville',
},
{
  type: 'periodical',
  volume: 1,
}, {
  type: 'music',
  genre: 'jazz',
}];

const bookSchema = Joi.object({
  type: Joi.string().valid('book'),
  author: Joi.string(),
});
const periodicalSchema = Joi.object({
  type: Joi.string().valid('periodical'),
  volume: Joi.number().integer(),
});
const musicSchema = Joi.object({
  type: Joi.string().valid('music'),
  genre: Joi.string(),
});
const payloadSchema = Joi.array().items(
  Joi.alternatives()
    .when(Joi.object({ type: Joi.string().valid('book').required() }).unknown().required(), { then: bookSchema })
    .when(Joi.object({ type: Joi.string().valid('periodical').required() }).unknown().required(), { then: periodicalSchema })
    .when(Joi.object({ type: Joi.string().valid('music').required() }).unknown().required(), { then: musicSchema })
    .when(Joi.any(), { then: musicSchema }),
);

const result = Joi.validate(payload, payloadSchema);
console.log(result);