How can I use Joi for advanced validation in my Node.js application?

How can I use Joi for advanced validation in my Node.js application?

You can use Joi to create complex validation schemas, including nested objects and custom validation rules. Would you like an example?

Yes, please provide an example of a nested object validation.

Sure! Here's a simple example:

const Joi = require('joi');

const schema = Joi.object({
  user: Joi.object({
    name: Joi.string().required(),
    age: Joi.number().integer().min(0).required()
  }).required()
});

const result = schema.validate({ user: { name: 'John', age: 30 } });
console.log(result);

This validates a user object with a name and age.

What if I want to add custom validation for the age?

You can use the .custom() method in Joi. For example:

const schema = Joi.object({
  user: Joi.object({
    name: Joi.string().required(),
    age: Joi.number().integer().min(0).custom((value, helpers) => {
      if (value < 18) {
        return helpers.error('any.invalid');
      }
      return value;
    }).required()
  }).required()
});

This will ensure the age is at least 18.