Node.js + Joi how to display a custom error messages?

Question

It seems pretty straight forward to validate user\'s input in Node.js RESTapi with Joi.

But the problem is that my app is not written in English. That m

Answer 1

Edit:

Make sure you are using @hapi/joi - https://www.npmjs.com/package/@hapi/joi, version 16 and above.

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Original answer:

The current way (I personally find it better) is to use .messages() (or .prefs({messages})).

const Joi = require('@hapi/joi');

const joiSchema = Joi.object({
  a: Joi.string()
    .min(2)
    .max(10)
    .required()
    .messages({
      'string.base': `"a" should be a type of 'text'`,
      'string.empty': `"a" cannot be an empty field`,
      'string.min': `"a" should have a minimum length of {#limit}`,
      'any.required': `"a" is a required field`
    })
});

const validationResult = joiSchema.validate({ a: 2 }, { abortEarly: false });
console.log(validationResult.error); // expecting ValidationError: "a" should be a type of 'text'

Usage of .errors() is not recommended just to update default message with custom message.

.prefs({ messages }) is an elaborate way to provide more options as preferences. The other options for prefs are taken directly from options of .validate()

Further read: https://github.com/hapijs/joi/issues/2158

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Update 1: I saw that the above explanation did not work out for some folks, so I have put up some code to test yourself. Check it here: https://runkit.com/embed/fnfaq3j0z9l2

Also updated the code snippet shared previously to have details from package inclusion, to usage, to calling the actual validation method.

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Update 2: The list of joi error types and their description (for .messages() - like string.base, array.unique, date.min etc..) is available here.