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Kenil Vasani
Kenil Vasani

Kenil Vasani

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Asked: 2020-12-19T22:01:13+00:00

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

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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 means I need to send a custom written messages to the frontend user.

I have googled for this and only found issues.

Maybe could someone give a solution for this?

This is the code I am using to validate with the Joi system:

    var schema = Joi.object().keys({
      firstName: Joi.string().min(5).max(10).required(),
      lastName: Joi.string().min(5).max(10).required()
      ..
    });

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

    function catched(reject) {
      res.json({
        validData: false,
        errors: reject
      });
    }

Plus, is there a way to use Joi in client side?

Thanks!

joinode.js
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    1 Answer

    1. Kenil Vasani

      Kenil Vasani

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      Best Answer

      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.

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