Posted on Jan 26 • Edited on Mar 7

Learning Node.js with Express.js: A Day-by-Day Guide

This document outlines a detailed day-by-day learning path to understand and practice Node.js with Express.js. By the end of the guide, you'll have created a project with login and signup functionality, including password hashing and token management.

Day 1: Introduction to Node.js

Topics:

What is Node.js and why use it?
Installing Node.js and npm
Understanding the Node.js runtime
Exploring Node.js modules and npm packages

Exercises:

Install Node.js and verify the installation with node -v and npm -v.
Create a "Hello World" application using Node.js.

Code:

// hello.js console.log('Hello, World!'); // Run using: node hello.js

Explore the fs and path modules with small examples.

Code:

const fs = require('fs'); const path = require('path'); // Create a file fs.writeFileSync('example.txt', 'This is an example'); // Read the file const data = fs.readFileSync('example.txt', 'utf-8'); console.log(data); // Get file path info console.log(path.basename('example.txt'));

Day 2: Setting Up Express.js

Topics:

Introduction to Express.js
Setting up a basic Express application
Understanding middleware and routes

Exercises:

Install Express.js using npm.

Command:

npm install express

Create a basic Express.js server with a "Hello World" route.

Code:

const express = require('express'); const app = express(); app.get('/', (req, res) => { res.send('Hello World!'); }); const PORT = 3000; app.listen(PORT, () => { console.log(`Server running on http://localhost:${PORT}`); });

Explore middleware by adding custom logging and error-handling middleware.

Code:

// Custom logging middleware app.use((req, res, next) => { console.log(`${req.method} ${req.url}`); next(); }); // Error-handling middleware app.use((err, req, res, next) => { console.error(err.stack); res.status(500).send('Something broke!'); });

Day 3: Routing and API Basics

Topics:

Understanding routes in Express.js
HTTP methods: GET, POST, PUT, DELETE
Using query parameters and route parameters

Exercises:

Create routes for basic CRUD operations.

Code:

app.get('/items', (req, res) => res.json({ message: 'Get all items' })); app.post('/items', (req, res) => res.json({ message: 'Create an item' })); app.put('/items/:id', (req, res) => res.json({ message: `Update item ${req.params.id}` })); app.delete('/items/:id', (req, res) => res.json({ message: `Delete item ${req.params.id}` }));

Build an API endpoint to return JSON data.

Code:

app.get('/api/data', (req, res) => { res.json({ id: 1, name: 'Example Item' }); });

Use Postman or a similar tool to test your routes.

Day 4: Working with Middleware

Topics:

Built-in middleware in Express.js
Third-party middleware (e.g., body-parser, cors)
Writing custom middleware

Exercises:

Use body-parser to parse incoming request bodies.

Code:

const bodyParser = require('body-parser'); app.use(bodyParser.json());

Add cors to your application for handling cross-origin requests.

Code:

const cors = require('cors'); app.use(cors());

Write a custom middleware function for logging request details.

Code:

app.use((req, res, next) => { console.log(`[${new Date().toISOString()}] ${req.method} ${req.url}`); next(); });

Day 5: Connecting to a Database (MongoDB)

Topics:

Introduction to MongoDB and Mongoose
Connecting your Node.js application to MongoDB
Defining and using schemas and models

Exercises:

Set up a local MongoDB instance or use MongoDB Atlas.
Install Mongoose and connect it to your MongoDB database.

Code:

const mongoose = require('mongoose'); mongoose.connect('mongodb://localhost:27017/mydatabase', { useNewUrlParser: true, useUnifiedTopology: true, }); mongoose.connection.once('open', () => { console.log('Connected to MongoDB'); });

Create a schema and model for user data.

Code:

const userSchema = new mongoose.Schema({ email: String, password: String, }); const User = mongoose.model('User', userSchema); module.exports = User;

Day 6: Password Hashing with bcrypt

Topics:

Why hash passwords?
Using the bcrypt library to hash and compare passwords

Exercises:

Install the bcrypt library.

Command:

npm install bcrypt

Create a function to hash a password before saving it to the database.

Code:

const bcrypt = require('bcrypt'); const hashPassword = async (password) => { const salt = await bcrypt.genSalt(10); return await bcrypt.hash(password, salt); }; // Usage const hashedPassword = await hashPassword('mypassword');

Write a function to compare hashed passwords during login.

Code:

const isMatch = await bcrypt.compare('mypassword', hashedPassword); console.log(isMatch); // true or false

Day 7: Token Management with JWT

Topics:

Introduction to JSON Web Tokens (JWT)
Creating and verifying JWTs
Storing and using tokens for authentication

Exercises:

Install the jsonwebtoken library.

Command:

npm install jsonwebtoken

Create a function to generate a token after a successful login.

Code:

const jwt = require('jsonwebtoken'); const generateToken = (userId) => { return jwt.sign({ id: userId }, process.env.JWT_SECRET, { expiresIn: '1h' }); }; const token = generateToken('12345'); console.log(token);

Add middleware to verify tokens for protected routes.

Code:

app.use((req, res, next) => { const token = req.headers.authorization?.split(' ')[1]; if (!token) return res.status(401).json({ message: 'Unauthorized' }); try { const decoded = jwt.verify(token, process.env.JWT_SECRET); req.user = decoded; next(); } catch (err) { res.status(401).json({ message: 'Invalid token' }); } });

Day 8: Creating the Login and Signup Features

Topics:

Building the signup route
Building the login route
Validating user input

Exercises:

Create a /signup route to register users and save hashed passwords.

Code:

app.post('/signup', async (req, res) => { const { email, password } = req.body; const hashedPassword = await hashPassword(password); const user = new User({ email, password: hashedPassword }); await user.save(); res.status(201).json({ message: 'User registered successfully' }); });

Create a /login route to authenticate users and return a token.

Code:

app.post('/login', async (req, res) => { const { email, password } = req.body; const user = await User.findOne({ email }); if (!user || !(await bcrypt.compare(password, user.password))) { return res.status(401).json({ message: 'Invalid credentials' }); } const token = generateToken(user._id); res.json({ token }); });

Add input validation using a library like express-validator.

Code:

const { body, validationResult } = require('express-validator'); app.post( '/signup', [body('email').isEmail(), body('password').isLength({ min: 6 })], async (req, res) => { const errors = validationResult(req); if (!errors.isEmpty()) { return res.status(400).json({ errors: errors.array() }); } const { email, password } = req.body; const hashedPassword = await hashPassword(password); const user = new User({ email, password: hashedPassword }); await user.save(); res.status(201).json({ message: 'User registered successfully' }); } );

The added code examples provide practical steps for each learning topic, ensuring hands-on practice throughout the journey.