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)))