How can I implement custom rules in Joi validation?

How can I implement custom rules in Joi validation?

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

Can you give me an example of a custom rule?

Sure! For instance, you can create a custom rule to validate a password strength by checking for a minimum length, uppercase letters, and special characters.

What does the code look like for that?

Here's a simple example:

const Joi = require('joi');

const passwordSchema = Joi.string().custom((value, helpers) => {
    const passwordRegex = /^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[!@#$%^&*])[A-Za-z\d!@#$%^&*]{8,}$/;
    if (!passwordRegex.test(value)) {
        return helpers.error('any.invalid');
    }
    return value;
});

How do I use this schema to validate a password?

You can use the schema like this:

const result = passwordSchema.validate('YourPassword123!');
if (result.error) {
    console.log(result.error.details);
} else {
    console.log('Password is valid!');
}