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

You can use .error(new Error('message')), And its work for me

var schema = Joi.object().keys({
  firstName: Joi.string().min(5).max(10).required().error(new Error('Give your error message here for first name')),
  lastName: Joi.string().min(5).max(10).required().error(new Error('Give your error message here for last name'))
  ..
});

Joi.validate(req.body, schema, function(err, value) {
  if (err) {
    console.log(err.message)
    return catched(err.message); 
  }
});

Answer 2

The best solution I found was :

Create a Middleware for JOI validation

Validator.js - You can create your custom error object

const Joi = require('Joi');

module.exports = schema => (req, res, next) => {
  const result = Joi.validate(req.body, schema);
  if (result.error) {
    return res.status(422).json({
      errorCause: result.error.name,
      missingParams: result.error.details[0].path,
      message: result.error.details[0].message
    });
  }
  next();
};

In the routes or controller pass this middleware function

const joiValidator = require('../utils/validator'); // Wherever you have declare the validator or middlerware

   const  userSchema = joi.object().keys({
    email : joi.string().email().required(),
    password : joi.string().required()
  });

  routes.routes('/').get(joiValidator(userSchema), (req, res) => {
    res.status(200).send('Person Check');
  });

Answer 3

Joi Version 14.0.0

const SchemaValidation = {
  coins: Joi.number()
    .required()
    .error(() => {
      return {
        message: 'Coins is required.',
      };
    }),
  challenge_name: Joi.string()
    .required()
    .error(() => {
      return {
        message: 'Challenge name is required.',
      };
    }),
  challengeType: Joi.string()
    .required()
    .error(() => {
      return {
        message: 'Challenge type is required.',
      };
    }),
  challengeDescription: Joi.string()
    .required()
    .error(() => {
      return {
        message: 'Challenge description is required.',
      };
    }),
};

In errors object you can get, error type and change message according.

Answer 4

Edit:

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

---

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

---

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.

---

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

Answer 5

Solution to add custom messages: Simply add another chained function to throw error while defining your schema.
In your case

 firstName: Joi.string().min(5).max(10).required().error(new Error('I am a custom error and I know it!')),

Rest will remain same.

Solution to use Joi at client side (Your 2nd question)

Joi-Browser is the package which enables usage of the same schema at the client side.

Here is an interesting discussion you can have a look at.

Cheers!

Answer 6

let schema = Joi.object({ foo: Joi.number().min(0).error(() => '"foo" requires a positive number') });

Docs link