micro-ajv

An Ajv (Another JSON Schema Validator) middleware for Micro to validate request body, url, query parameters and etc.

Installation

npm install --save micro-ajv

Usage

By default, it validates request body and replies with 400 status code if validation fails.

const { send } = require('micro')
const microAjvValidation = require('micro-ajv')

const schema = { type: 'string', maxLength: 1024 }
const validate = microAjvValidation(schema)

const handler = (req, res) => send(res, 200, 'Ok')

module.exports = validate(handler)

Middleware Options

It's possible to configure the middleware behavior by passing options object

Option	Description	Default
ajv	Ajv options	{}
target	Path to data for validations (e.g. query.accountId). It validates request body by default	"body"
errorMode	Enables change middleware behavior strategy when request validation fails. There are three possible modes: reply — respond with an error; throw — throw an exception; inject – call handler with injected validation errors to the req object	"reply"
injectKey	Enables pass validation errors to the req object when error mode is inject	"microAjvErrors"
createError	Use this option if you need to change the default error object. As a first argument, it expects Ajv validation errors	errors => micro.createError(400, 'Bad request')

Examples

Validate req.url and handle validation errors inside the handler:

const { send } = require('micro')
const microAjvValidation = require('micro-ajv')

const schema = { type: 'string', maxLength: 1024 }
const options = { target: 'url', errorMode: 'inject', injectKey: 'errors' }
const validate = microAjvValidation(schema, options)

module.exports = validate((req, res) => {
  console.error(req.errors)
  send(res, 414, 'Request url is too long')
})

Validate req.body and reply with a custom error if it fails

const { send } = require('micro')
const microAjvValidation = require('micro-ajv')

const schema = { type: 'string', maxLength: 1024 }
const options = {
  createError: errors =>
    Object.assign(Error(errors.map(error => error.message)), { statusCode: 400 }),
}

const validate = microAjvValidation(schema, options)

const handler = (req, res) => send(res, 200, 'Ok')

module.exports = validate(handler)

Sometime you may need to throw an exception and probably catch it somewhere else in the project instead of replying with an error immediately.

// handler.js
const { send } = require('micro')
const microAjvValidation = require('micro-ajv')

const schema = { type: 'string', maxLength: 1024 }
const options = {
  errorMode: 'throw',
  createError: errors =>
    Object.assign(Error('Payload validation failed'), { type: 'ApiError', statusCode: 400 }),
}
const validate = microAjvValidation(schema, options)

const handler = (req, res) => send(res, 200, 'Ok')

module.exports = validate(handler)

// middleware.js
module.exports.logApiErrors = handler => (req, res) =>
  handler(req, res).catch(err => {
    if (err.type === 'ApiError') {
      console.log(`ApiError: ${err.message}`)
    }
    throw err
  })

// index.js
const { router, post } = require('microrouter')
const { logApiErrors } = require('./middleware')
const handler = require('./handler')

module.exports = logApiErrors(router(post('/foo', handler)))