Validating schema with Yup!

João Hencke — Fri, 06 Sep 2019 01:28:15 +0000

Do you think validate types in JavaScript is boring?
Have you heard about Yup? It's an amazing JavaScript lib to validate schemas!

Let's imagine:

We have a list products endpoint, which takes the page number and limit as arguments from querystring

//productApi.js
const { Router } = require('express');
const productController = require('./controller');

const router = new Router();

module.exports = app => app.use('/products', router);

router.get('/', (req, res, next) => {
  const { page, limit } = req.query;

  if (isNaN(page) || isNaN(limit)) return res.status(400).end();

  productController.list({ page: Number(page), limit: Number(limit) })
    .then(products => res.json(products))
    .catch(error => res.status(400).json({ error }));
}

The problem is: page and limit can be undefined and... anything else... it's javascript baby.

A very efficient way is to create a middleware to validate your params using Yup.

//validate.js
const yup = require('yup');

module.exports = ({ shape, path = 'query' }) => async (req, res, next) => {
  const schema = yup.object().shape(shape);

  try {
    const validData = await schema.validate(req[path]);
    req.validData = validData;
    return next();
  } catch (error) {
    return res.status(400).json({ error });
  }
};

After then, use on route

//productApi.js
const { Router } = require('express');
const yup = require('yup');
const validate = require('./validate');
const productController = require('./controller');

const router = new Router();

module.exports = app => app.use('/products', router);

router.get(
  '/',
  validate({
    shape: {
      page: yup.number().default(0),
      limit: yup.number().default(15),
    }
  }),
  (req, res, next) => {
    productController
      .list(req.validData)
      .then(products => res.json(products))
      .catch(error => res.status(400).json({ error }));
  },
);

Of course you can create complex schemas with Yup. It works as you need.

I hope it helps someone!

DEV Community: João Hencke

Validating schema with Yup!