Joi Error Msg

A helper to show Joi errors as nicely formatted strings

Joi's validation functions retrieve detailed errors when schemas are not validated. But they are not ready to be shown to your users.

• The validate function returns error details without throwing:

const { error, value } = Joi.number().integer().validate(5.5)

/*
{
  value: 5.5,
  error: [Error [ValidationError]: "value" must be an integer] {
    _original: 5.5,
    details: [
      {
        message: '"value" must be an integer',
        path: [],
        type: 'number.integer',
        context: { label: 'value', value: 5.5 }
      }
    ]
  }
}
*/

• The assert function lets you throw errors when a schema is not validated:

Joi.assert(5.5, Joi.number().integer())

/*
Uncaught Error [ValidationError]: "value" must be an integer
    at Object.exports.process (/some/project/node_modules/.pnpm/joi@17.6.0/node_modules/joi/lib/errors.js:193:16)
    at Object.internals.entry (/some/project/node_modules/.pnpm/joi@17.6.0/node_modules/joi/lib/validator.js:153:26)
    at Object.exports.entry (/some/project/node_modules/.pnpm/joi@17.6.0/node_modules/joi/lib/validator.js:27:30)
    at internals.Base.validate (/some/project/node_modules/.pnpm/joi@17.6.0/node_modules/joi/lib/base.js:548:26)
    at Object.internals.assert (/some/project/node_modules/.pnpm/joi@17.6.0/node_modules/joi/lib/index.js:225:27)
    at Object.assert (/some/project/node_modules/.pnpm/joi@17.6.0/node_modules/joi/lib/index.js:102:19) {
  _original: 5.5,
  details: [
    {
      message: '"value" must be an integer',
      path: [],
      type: 'number.integer',
      context: [Object]
    }
  ]
}
*/

• The attempt function will return value if ok, and throw if not:

const x = Joi.attempt(5.5, Joi.number().integer())

/*
Uncaught Error [ValidationError]: "value" must be an integer
    at Object.exports.process (/some/project/node_modules/.pnpm/joi@17.6.0/node_modules/joi/lib/errors.js:193:16)
    at Object.internals.entry (/some/project/node_modules/.pnpm/joi@17.6.0/node_modules/joi/lib/validator.js:153:26)
    at Object.exports.entry (/some/project/node_modules/.pnpm/joi@17.6.0/node_modules/joi/lib/validator.js:27:30)
    at internals.Base.validate (/some/project/node_modules/.pnpm/joi@17.6.0/node_modules/joi/lib/base.js:548:26)
    at Object.internals.assert (/some/project/node_modules/.pnpm/joi@17.6.0/node_modules/joi/lib/index.js:225:27)
    at Object.assert (/some/project/node_modules/.pnpm/joi@17.6.0/node_modules/joi/lib/index.js:102:19) {
  _original: 5.5,
  details: [
    {
      message: '"value" must be an integer',
      path: [],
      type: 'number.integer',
      context: [Object]
    }
  ]
}
*/

Usage

import Joi from 'joi'
import { validate, assert, multiAssert, attempt } from 'joi-error-msg'

// validate (value, schema, mentionWrongValueWith = '')
// Gets error msg, if any
let errorMsg = validate('a', Joi.number().integer().label('Value')) // use joi's label to define value's name
/* '➤ Value must be a number' */
validate('b', Joi.number().integer().label('Height'), 'is no good!')
/* '➤ "b" is no good! Height must be a number' */

// assert (titleMsg = '', value, schema, mentionWrongValueWith = '', titleMsg = '')
// Throw if error
try {
  const schema = Joi.array().min(1).items(
      Joi.valid('A', 'B', 'C').label('Value')
    ).label('Values')

  assert(['D'], schema, '', 'Error checking values!')
} catch (e) {
  console.error(e)
}
/*
Error checking values!
➤ Value must be one of [A, B, C]
*/

// multiAssert (titleMsg = '', ...validates)
// Validate multiple schemas, and throw if any errors
try {
  multiAssert('Error defining graph!',
    validate('a', Joi.number().integer().required().label('X coordinate')),
    validate('b', Joi.number().integer().required().label('Y coordinate'))
  )
} catch (e) {
  console.error(e)
}
/*
Error: Error defining graph!
➤ X coordinate must be a number
➤ Y coordinate must be a number
*/

// attempt (titleMsg = '', value, schema, mentionWrongValueWith = '', titleMsg = '')
try {
  let x = attempt(3, Joi.number().integer().required().label('Value'), 'is wrong.')
  /* x = 3 */

  x = attempt('a', Joi.number().integer().required().label('Value'), 'is wrong.')
} catch (e) {
  console.error(e)
}
/* '➤ "a" is wrong. Value must be a number' */

Advanced usage

The bullets in error list can be configured. E.g.:

import { config as joiMsgConfig } from 'joi-error-msg'

joiMsgConfig({ bullet: '*' })

Error messages can be colored with functions. For example, simply use chalk

import { config as joiMsgConfig } from 'joi-error-msg'
import chalk from 'chalk'

joiMsgConfig({ color: chalk.yellow, titleColor: chalk.red })

Note that if you already have a Joi error, you could use just the error formatting function:

import Joi from 'joi'
import errorMsg from 'joi-error-msg'
// errorMsg (joiError, mentionWrongValueWith = '')

const { error, value } = Joi.number().integer().validate(5.5)
if (error) console.error(errorMsg(error))

Other projects similar to this

• joi-summarize
• joi-error-formatter
• joi-message
• make-joiful-errors
• custom-joi-error