Joi validator conditional schema

I achieved the same in a little different manner. Posting the same here since this might be useful for someone in future.

const schema = Joi.object({
    type: Joi.number().required().valid(1, 2, 3),
    firstname: Joi.alternatives().conditional('type', { is: 1, then: Joi.string().required() }),
    lastname: Joi.alternatives().conditional('type', { is: 1, then: Joi.string().required() }),
    salary: Joi.alternatives().conditional('type', { is: 2, then: Joi.number().required() }),
    pension: Joi.alternatives().conditional('type', { is: 2, then: Joi.number().required() }),
    credit: Joi.alternatives().conditional('type', { is: 3, then: Joi.number().required() }),
    debit: Joi.alternatives().conditional('type', { is: 3, then: Joi.number().required() }),
}))

This was working perfectly as expected.

When the type value is 1 the object should have only type, firstname and lastname

When the type value is 2 the object should have only type, salary and pension

When the type value is 3 the object should have only type, credit and debit

Any other combination will be thrown as error from the joi validator middleware layer. Also any other type value other that 1, 2 and 3 will be throwing error.

It works for me!

var Joi = require('joi');

var schema = {
    a: Joi.any().when('b', { is: 5, then: Joi.required(), otherwise: Joi.optional() }),
    b: Joi.any()
};

var thing = {
    b: 5
};
var validate = Joi.validate(thing, schema);

// returns
{
    error: null,
    value: {
        b: 5
    }
}

This is the reference.