How to compare password and confirm password inputs using express-validator ?

Last Updated : 25 Dec, 2023

Registration or Sign Up on any website always requires a confirmed password input and it must be the same as the password. It is basically to ensure that the user enters the password full of his senses and there is no conflict happening. This functionality can be implemented anywhere in our code like in the index file or route file but this comes under the validation part. So we usually prefer to code this logic where all the other validations are coded. Here we use 'express-validator' middleware to implement this functionality.

Prerequisites

Approach to compare and confirm password:

Create a validator.js file to code all the validation logic.
Validate confirmPassword by validateConfirmPassword: check('confirmPassword') and chain on all the validation with ' . '
Use the validation name(validateConfirmPassword) in the routes as a middleware as an array of validations.
Destructure 'validationResult' function from express-validator to use it to find any errors
If the error occurs redirect to the same page passing the error information
If the error list is empty, give access to the user for the subsequent request.

Steps to create application and installing required dependencies

Step 1: Initialized an express app for the project

npm init -y

Step 2: Install the required dependencies

npm i express express-validator body-parser nodemon

Folder Structure:

The updated dependencies in package.json file will look like:

"dependencies": {
    "body-parser": "^1.19.0",
    "express": "^4.17.1",
    "express-validator": "^6.6.0",
    "nodemon": "^2.0.4"
}

Example : This example illustrates how to check if email address is already in use or not for a particular website.

javascript

//index.js

const express = require('express')
const bodyParser = require('body-parser')
const { validationResult } = require('express-validator')
const repo = require('./repository')
const { validateConfirmPassword } = require('./validator')
const signupTemplet = require('./signup')

const app = express()

const port = process.env.PORT || 3000

// The body-parser middleware to parse form data
app.use(bodyParser.urlencoded({ extended: true }))


// Get route to display HTML form to sign in
app.get('/signup', (req, res) => {
    res.send(signupTemplet({}))
})

// Post route to handle form submission logic and 
app.post(
    '/signup',
    [validateConfirmPassword],
    async(req, res) => {
    const errors = validationResult(req)
    if (!errors.isEmpty()) {
        return res.send(signupTemplet({ errors }))
    }
    const { email, password } = req.body
    await repo.create({ email, password })
    res.send('Sign Up successfully')
})

// Server setup
app.listen(port, () => {
    console.log(`Server start on port ${port}`)
})

JavaScript

//repository.js 

const fs = require('fs')

class Repository {
    constructor(filename) {

        // The filename where datas are
        // going to store
        if (!filename) {
            throw new Error(
                'Filename is required to create a datastore!')
        }
        this.filename = filename
        try {
            fs.accessSync(this.filename)
        } catch (err) {

            // If file not exist it is 
            // created with empty array
            fs.writeFileSync(this.filename, '[]')
        }
    }

    // Get all existing records
    async getAll() {
        return JSON.parse(
            await fs.promises.readFile(this.filename, {
                encoding: 'utf8'
            })
        )
    }

    // Find record by properties
    async getOneBy(filters) {
        const records = await this.getAll()
        for (let record of records) {
            let found = true
            for (let key in filters) {
                if (record[key] !== filters[key]) {
                    found = false
                }
            }
            if (found) return record;
        }
    }

    // Create new record
    async create(attrs) {
        const records = await this.getAll()
        records.push(attrs)
        await fs.promises.writeFile(
            this.filename,
            JSON.stringify(records, null, 2)
        )
        return attrs
    }
}

// The 'datastore.json' file created at runtime 
// and all the information provided via signup form
// store in this file in JSON format.
module.exports = new Repository('datastore.json')

JavaScript

//signup.js

const getError = (errors, prop) => {
    try {
        return errors.mapped()[prop].msg;
    } catch (error) {
        return "";
    }
};

module.exports = ({ errors }) => {
    return `
      <!DOCTYPE html>
      <html>
        <head>
          <link rel='stylesheet'
href='https://cdnjs.cloudflare.com/ajax/libs/bulma/0.9.0/css/bulma.min.css'>
          <style>
            div.columns {
              margin-top: 100px;
            }
            .button {
              margin-top: 10px;
            }
          </style>
        </head>
        <body>
          <div class='container'>
            <div class='columns is-centered'>
              <div class='column is-5'>
                <h1 class='title'>Sign Up</h1>
                <form method='POST'>             
                  <div>
                    <div>
                      <label class='label' id='email'>
                        Username</label>
                    </div>
                    <input class='input' type='text'
                           name='email'
                           placeholder='Email' for='email'>
                  </div>
                  <div>
                    <div>
                      <label class='label' id='password'>
                        Password</label>
                    </div>
                    <input class='input' type='password'
                           name='password'
                           placeholder='Password' for='password'>
                  </div>
                  <div>
                    <div>
                      <label class='label' id='confirmPassword'>
                        Confirm Password</label>
                    </div>
                    <input class='input' type='password'
                           name='confirmPassword'
                           placeholder='Confirm Password' 
                           for='confirmPassword'>
                    <p class="help is-danger">
                      ${getError(errors, "confirmPassword")}
                    </p>
                  </div>
                  <div>
                    <button class='button is-primary'>
                      Sign Up
                    </button>
                  </div>
                </form>
              </div>
            </div>
          </div>
        </body>
      </html>   
    `;
};

JavaScript

//validator.js 

const { check } = require('express-validator')
const repo = require('./repository')
module.exports = {

    validateConfirmPassword: check('confirmPassword')

        // To delete leading and trailing space
        .trim()

        // Validate minimum length of password
        // Optional for this context
        .isLength({ min: 4, max: 16 })

        // Custom message
        .withMessage('Password must be between 4 to 16 characters')

        // Custom validation
        // Validate confirmPassword
        .custom(async(confirmPassword, { req }) => {
    const password = req.body.password;

    // If password and confirm password not same
    // don't allow to sign up and throw error
    if (password !== confirmPassword) {
        throw new Error('Passwords must be same')
    }
})
}