express-validator setup - Mini Project: Build & Apply

express-validator setup

📖 Scenario: You are building a simple Express server that needs to check user input for a registration form. To keep the server safe and clean, you want to add validation to the input fields.

🎯 Goal: Set up express-validator in an Express app to validate a user's email and password fields in a POST request.

📋 What You'll Learn

Create an Express app with express imported

Import express-validator functions check and validationResult

Add a POST route /register that uses check to validate email and password

Use validationResult to handle validation errors in the route

💡 Why This Matters

🌍 Real World

Validating user input on the server helps prevent bad data and security issues in web applications.

💼 Career

Express-validator is a common tool used by backend developers to ensure data integrity and improve app reliability.

1

Create Express app and import express-validator

Create a variable called express by requiring the 'express' package. Then create an Express app by calling express() and assign it to a variable called app. Next, import check and validationResult from the 'express-validator' package using destructuring assignment.

Express

const express = require('express');
const app = express();
const { check, validationResult } = require('express-validator');
// Your code here

Need a hint?

Use require('express') to import Express and require('express-validator') to import the validator functions.

2

Add middleware to parse JSON body

Add middleware to the Express app by calling app.use(express.json()) to enable JSON body parsing for incoming requests.

Express

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

// Add JSON body parser middleware
// Your code here

Need a hint?

Use app.use(express.json()) to parse JSON bodies sent by clients.

3

Create POST /register route with validation checks

Create a POST route on /register using app.post. Add validation middleware using check to validate the email field is a valid email and the password field has a minimum length of 6 characters.

Express

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

app.use(express.json());

// Create POST /register route with validation
// Your code here

Need a hint?

Use app.post('/register', [check(...), check(...)], (req, res) => { ... }) to add validation middleware.

4

Handle validation results and send response

Inside the POST /register route handler, use validationResult(req) to get validation errors. If there are errors, respond with status 400 and a JSON object containing the errors. Otherwise, respond with status 200 and a JSON message { message: 'User registered successfully' }.

Express

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

app.use(express.json());

app.post('/register', [
  check('email').isEmail(),
  check('password').isLength({ min: 6 })
], (req, res) => {
  // Use validationResult to check for errors
  // Your code here
});

Need a hint?

Use validationResult(req) to get errors, check if empty, and respond accordingly.