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.

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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:

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

Code:

// hello.js
console.log('Hello, World!');

// Run using: node hello.js

1. 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'));

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Day 2: Setting Up Express.js

Topics:

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

Exercises:

1. Install Express.js using npm.

Command:

npm install express

1. 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}`);
});

1. 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!');
});

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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:

1. 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}` }));

1. Build an API endpoint to return JSON data.

Code:

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

1. Use Postman or a similar tool to test your routes.

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Day 4: Working with Middleware

Topics:

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

Exercises:

1. Use body-parser to parse incoming request bodies.

Code:

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

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

Code:

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

1. 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();
});

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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:

1. Set up a local MongoDB instance or use MongoDB Atlas.
2. 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');
});

1. 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;

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Day 6: Password Hashing with bcrypt

Topics:

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

Exercises:

1. Install the bcrypt library.

Command:

npm install bcrypt

1. 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');

1. Write a function to compare hashed passwords during login.

Code:

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

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Day 7: Token Management with JWT

Topics:

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

Exercises:

1. Install the jsonwebtoken library.

Command:

npm install jsonwebtoken

1. 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);

1. 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' });
  }
});

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Day 8: Creating the Login and Signup Features

Topics:

• Building the signup route
• Building the login route
• Validating user input

Exercises:

1. 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' });
});

1. 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 });
});

1. 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' });
  }
);

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