node js parameter validation code example

Example 1: express validator example

// this method create custom express validator using middleware

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

exports.resultsValidator = (req) => {
  const messages = []
  if (!validationResult(req).isEmpty()) {
    const errors = validationResult(req).array()
    for (const i of errors) {
      messages.push(i)
    }
  }
  return messages
}

exports.registerValidator = () => {
  return [
    check('username')
      .notEmpty()
      .withMessage('username is required')
      .not()
      .custom((val) => /[^A-za-z0-9\s]/g.test(val))
      .withMessage('Username not use uniq characters'),
    check('password')
      .notEmpty()
      .withMessage('password is required')
      .isLength({ min: 8 })
      .withMessage('password must be 8 characters')
  ]
}

exports.loginValidator = () => {
  return [
    check('username').notEmpty().withMessage('username or email is required'),
    check('password').notEmpty().withMessage('password is required')
  ]
}

// how to use express validator in controller for results message
const errors = resultsValidator(req)
  if (errors.length > 0) {
    return res.status(400).json({
      method: req.method,
      status: res.statusCode,
      error: errors
    })
  }

// how to use express validator in route
route.post('/login', loginValidator(), (req, res) => {
   return res.status(200).send('Login Sucessfuly');
});

route.post('/register', registerValidator(), (req, res) => {
   return res.status(200).send('Register Sucessfuly');
});

Example 2: example of validating fields on your own in express

const User = require('./models/user')

exports.createUser = (req, res, next) => {
  /** Here you need to validate user input. 
   Let's say only Name and email are required field
 */
  
  const { userName, email, phone, status } = req.body
  if (userName && email &&  isValidEmail(email)) { 
    
    // isValidEmail is some custom email function to validate email which you might need write on your own or use npm module
    User.create({
      userName,
      email,
      phone,
      status,   
    })
    .then(user => res.json(user))
    .catch(next)
  }
}