User registration flow in Express - Mini Project: Build & Apply

User registration flow

📖 Scenario: You are building a simple user registration flow for a website using Express.js. Users will send their username and password to register.

🎯 Goal: Create an Express.js server that accepts user registration data, validates it, and stores it in memory.

📋 What You'll Learn

Create an Express app instance

Set up a route to accept POST requests at /register

Store registered users in an in-memory array

Validate that username and password are provided

Send appropriate success or error responses

💡 Why This Matters

🌍 Real World

User registration is a common feature in web apps to create accounts and manage access.

💼 Career

Understanding how to build backend routes for user registration is essential for web developers working with Node.js and Express.

1

Set up Express app and users array

Create an Express app by requiring express and calling express(). Then create an empty array called users to store registered users.

Express

const express = require('express');
const app = express();

// Your code here

Need a hint?

Use require('express') to import Express and call it to create the app. Then declare users as an empty array.

2

Add JSON body parsing middleware

Add middleware to the Express app to parse incoming JSON request bodies by calling app.use(express.json()).

Express

const express = require('express');
const app = express();

const users = [];

// Your code here

Need a hint?

Use app.use(express.json()) to enable JSON body parsing for POST requests.

3

Create POST /register route with validation

Create a POST route at /register using app.post. Inside the route handler, extract username and password from req.body. If either is missing, respond with status 400 and JSON { error: 'Username and password required' }. Otherwise, add an object with username and password to the users array and respond with status 201 and JSON { message: 'User registered' }.

Express

const express = require('express');
const app = express();

const users = [];

app.use(express.json());

// Your code here

Need a hint?

Use app.post('/register', (req, res) => { ... }). Extract username and password from req.body. Check if either is missing and respond with 400 and error JSON. Otherwise, add the user to users and respond with 201 and success JSON.

4

Start the server listening on port 3000

Add code to start the Express app listening on port 3000 by calling app.listen(3000). Add a callback that logs 'Server running on port 3000'.

Express

const express = require('express');
const app = express();

const users = [];

app.use(express.json());

app.post('/register', (req, res) => {
    const { username, password } = req.body;
    if (!username || !password) {
        return res.status(400).json({ error: 'Username and password required' });
    }
    users.push({ username, password });
    res.status(201).json({ message: 'User registered' });
});

// Your code here

Need a hint?

Use app.listen(3000, () => { console.log('Server running on port 3000'); }) to start the server.