How to implement validation in a separate file using express-validator

Question

I am trying to use express-validator to validate the req.body before sending a post request to insert data to postgres.

I have a route file, controller file and I want to carryout validation in a file called validate.js. Meanwhile, I have installed express-validator and in my server.js I have imported it. Other resources I come across seem to implement the validation in the function that contains the logic for inserting the data.

//server.js
....
import expressValidator from 'express-validator';

...
app.use(bodyParser.urlencoded({ extended: false }));
app.use(expressValidator);

//route.js
import express from 'express';
import usersController from './controller';

const router = express.Router();

router.post('/createuser', usersController.createUser);

//controller.js
createUser(req, res){
  // ...
  const { firstName, lastName, email, password } = req.body;
  //code to insert user details to the database
}

//validator.js
import { check } from 'express-validator/check';

module.exports = [check('email').isEmail()];

I expect to implemet the validation in a file called validator.js to, say, validate the email before inserting to the database

What is the value of the `action` attribute of your form? – Razvan Zamfir Mar 16 '20 at 13:45 — Razvan Zamfir, Mar 16 '20 at 13:45

score 45 · Answer 1 · edited Oct 12 '20 at 09:17

I have same approach, except one thing that is we shouldn't handle validation error in our controller. So If any error is occurring at Validation Layer, it should throw back from there only. We shouldn't allow our control flow to enter into the Controller Layer. So below are the code example:

useRoute.js

const route = express.Router();

const {
  **validateUser**,
} = require('../middlewares/validators/userValidator');

route.route('/').post(**validateUser**, createUser);
route.route('/:id').put(**validateUser**, updateUser);

module.exports = route;

userValidator.js

const {check, validationResult} = require('express-validator');

exports.validateUser = [
  check('name')
    .trim()
    .escape()
    .not()
    .isEmpty()
    .withMessage('User name can not be empty!')
    .bail()
    .isLength({min: 3})
    .withMessage('Minimum 3 characters required!')
    .bail(),
  check('email')
    .trim()
    .normalizeEmail()
    .not()
    .isEmpty()
    .withMessage('Invalid email address!')
    .bail(),
  (req, res, next) => {
    const errors = validationResult(req);
    if (!errors.isEmpty())
      return res.status(422).json({errors: errors.array()});
    next();
  },
];

controller.js

/**
 * @desc    - create new User
 * @method  - POST
 */
exports.createCategory = async (req, res) => {
  //  do your stuff here. (No need to check any validation error here)
}

While the solution works, I would discourage following the advice of handing the error in the validator instead of the controller — Max O., Apr 09 '22 at 19:57

dimitris tseggenes · Answer 2 · 2019-04-20T13:31:39.643

13

Here is the way i use express-validator. I have a file validator.js where i have validation logic for many routes. For example:

validator.js

const { check } = require('express-validator/check');

exports.createUser = [check('email').isEmail()];

exports.anotherRoute = [// check data];

exports.doSomethingElse = [// check data];

Now in your route file you require the validator.js file
const validator = require("./validator"); // or where your file is located
and use the validation logic you want as a middleware. For example:

route.js

//

router.post('/createuser', validator.createUser, usersController.createUser);

Last, inside your controller you have to check for possible errors created during validation, after requiring validationResult.

controller.js

const { validationResult } = require('express-validator/check');


exports.createUser(req, res) {
    const errors = validationResult(req);
    if (!errors.isEmpty()) {
        return res.status(422).json({ errors: errors.array() });
    }
    // do stuff here.

}

Also, you don't have to use app.use(expressValidator); in your server.js file

edited Apr 20 '19 at 13:31

answered Apr 20 '19 at 12:16

dimitris tseggenes

3,031
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Thanks @dimitris I tried the solution you gave, and I don't get anything inserted into the database and I dont get any errors, the request like takes forever. – Micah Bala Apr 20 '19 at 13:12
No I did not alter the controller or check for any errors – Micah Bala Apr 20 '19 at 13:17
Works great! Thankss – Oscar R Sep 12 '19 at 20:28
hello i'm new to node can i ask why you used the brackets instead of callback function – S.alhaider May 01 '20 at 23:48
What's the reason behind not letting the validator middleware throw the error? – Florian Walther Mar 02 '23 at 11:01
In most cases it's better to let the middleware throw the error. But in a few cases I want to follow another error handling policy, so I implement it inside the controller. – dimitris tseggenes Mar 02 '23 at 13:07

score 5 · Answer 3 · answered Sep 06 '20 at 17:38

I was running into a few problems with async functions, here is my humble solution hope this helps someone:

Route Definitions

const router = require('express').Router();

const userValidator = require('./Validators/UserValidator');
const userController = require('./Controllers/UserController');

router.post('/users', userValidator.add, userController.add);

Validator

const { check, validationResult } = require('express-validator');

const generateValidators = () => [
    check('first_name')...,
    
    check('last_name')...,
    
    check('email')...,
    
    check('password')...
]

const reporter = (req, res, next) => {
    const errors = validationResult(req);

    if (!errors.isEmpty()) {
        const errorMessages = errors.array().map(error => error.msg);
        
        return res.status(400).json({
            errors: errorMessages
        });
    }
    
    next();
}

module.exports = {
    add: [
        generateValidators(),
        reporter
    ]
};

What if I want to pass rules in generateValidators conditionally o basis which action user has passed in req object (in api case) ? — Davinder Kumar, Feb 22 '21 at 10:02

score 0 · Answer 4 · answered Oct 04 '21 at 12:19

just adding few changes to Shivam's answer for

email

const {check, validationResult} = require('express-validator');

exports.validateUser = [
  check('name')
    .trim()
    .escape()
    .not()
    .isEmpty()
    .withMessage('User name can not be empty!')
    .bail()
    .isLength({min: 3})
    .withMessage('Minimum 3 characters required!')
    .bail(),
  check('email')
    trim()
.not()
.isEmpty()
.withMessage("Email name can not be empty!")
.bail()
.isEmail()
.withMessage("Invalid email address!")
.bail(),
  (req, res, next) => {
    const errors = validationResult(req);
    if (!errors.isEmpty())
      return res.status(422).json({errors: errors.array()});
    next();
  },
];

How to implement validation in a separate file using express-validator

4 Answers4

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