express-masterclass

A comprehensive Express.js guide covering routing, request & response handling, custom middleware, CRUD operations, template engines, error handling, third-party NPM packages, controllers, frontend data fetching, and environment variables. Perfect for building robust backend applications.

📌 What is Express?

Minimal and flexible web framework for Node.js.
Used for building server-side web applications and APIs.
The most popular framework for Node.js.
Simplifies the process of handling HTTP requests and responses.
Express is a very fast and unopinionated framework.

📚 Prerequisites

JavaScript Fundamentals (Functions, Loops, Objects, Classes, etc.).
HTTP Basics (Methods, Status Codes, etc.).
Understanding of JSON APIs.
Basic knowledge of Node.js.
Familiarity with NPM (Node Package Manager).

📖 Syllabus

Routing - Creating and managing routes.
Request & Response - Handling incoming requests and sending responses.
Custom Middleware - Building reusable middleware functions.
CRUD Operations - Implementing Create, Read, Update, and Delete functionalities.
Template Engines - Using templating systems like EJS, Pug, etc.
Error Handling - Managing errors and providing meaningful messages.
3rd Party NPM Packages - Integrating external packages for extended functionality.
Controllers - Structuring code for maintainability.
Fetching From Frontend - Handling frontend requests and sending appropriate responses.
Environment Variables - Securing and managing sensitive information.

📌 Topics Explanation & Code Samples

6. Error Handling

// Middleware for handling errors
function errorHandler(err, req, res, next) {
    console.error(err.message);
    res.status(500).json({ error: 'Something went wrong!' });
}

app.use(errorHandler);

7. 3rd Party NPM Packages (Example: Morgan)

npm install morgan

const morgan = require('morgan');
app.use(morgan('dev'));  // Logs requests to the console

8. Controllers (Organizing Your Code)

// controllers/userController.js
exports.getUsers = (req, res) => {
    res.json(users);
};

exports.createUser = (req, res) => {
    const user = req.body;
    users.push(user);
    res.status(201).json(user);
};

// routes/userRoutes.js
const express = require('express');
const router = express.Router();
const userController = require('../controllers/userController');

router.get('/', userController.getUsers);
router.post('/', userController.createUser);

module.exports = router;

// app.js
const userRoutes = require('./routes/userRoutes');
app.use('/users', userRoutes);

9. Fetching From Frontend

<!-- public/index.html -->
<!DOCTYPE html>
<html>
<head>
    <title>Frontend Form</title>
</head>
<body>
    <form id="userForm">
        <input type="text" id="name" placeholder="Enter name" required />
        <input type="number" id="age" placeholder="Enter age" required />
        <button type="submit">Submit</button>
    </form>

    <script>
        document.getElementById('userForm').addEventListener('submit', async (e) => {
            e.preventDefault();
            const name = document.getElementById('name').value;
            const age = document.getElementById('age').value;

            const response = await fetch('/users', {
                method: 'POST',
                headers: {
                    'Content-Type': 'application/json'
                },
                body: JSON.stringify({ name, age })
            });

            const result = await response.json();
            alert(`User ${result.name} added successfully!`);
        });
    </script>
</body>
</html>

10. Environment Variables

# Install dotenv package
npm install dotenv

// app.js
require('dotenv').config();

const PORT = process.env.PORT || 3000;
app.listen(PORT, () => console.log(`Server running at http://localhost:${PORT}`));

# .env
PORT=4000

📂 Folder Structure (Updated)

express-masterclass/
│
├── controllers/
├── middlewares/
├── models/
├── public/
├── routes/
├── views/
├── .env
├── app.js
├── package.json
└── README.md

✅ Complete Setup

Clone the repository:

git clone https://github.com/ExploitEngineer/express-masterclass.git

Install dependencies:
```
npm install
```
Start the server:
```
npm run dev
```

Your Express.js project is now fully set up with Routing, Middleware, CRUD Operations, Templating, Error Handling, Controllers, Environment Variables, and Fetching from Frontend.