How can I use Joi with TypeScript for custom types?

How can I use Joi with TypeScript for custom types?

You can create custom types in Joi by using the Joi.extend() method. This allows you to define new validation rules.

Can you show me an example of a custom type?

Sure! Here's a simple example:

import Joi from 'joi';

const customJoi = Joi.extend((joi) => ({
  type: 'customType',
  base: joi.string(),
  messages: {
    'customType.base': '{{#label}} must be a custom type!'
  },
  validate(value, helpers) {
    if (value !== 'expectedValue') {
      return { value, errors: helpers.error('customType.base') };
    }
  }
}));

const schema = customJoi.customType();
const result = schema.validate('someValue');

What if I want to add multiple custom validations?

You can chain multiple validations together in Joi. Just add them in the schema definition like this:

const schema = customJoi.customType().min(5).max(10);