Express: Basics and Getting Started

Express is a minimalist framework for Node.js that makes backend development approachable. It helps you understand HTTP fundamentals and build robust servers quickly.

Express Fundamentals

HTTP Server

Express wraps Node’s native http module, making it easier to create servers that listen for requests and send responses.

Request & Response Objects

• Request (req): Contains client data (URL, method, headers, body).
• Response (res): Used to send data back (text, JSON, files, status codes).

app.get('/hello', (req, res) => {
    res.json({ message: 'Hello, this is a JSON response' });
});

Routing

Routes define how your server responds to different endpoints and HTTP methods.

app.get('/users', (req, res) => {
    res.json({ users: [] });
});

app.post('/users', (req, res) => {
    res.status(201).json({ message: 'User created' });
});

Middleware

Middleware functions run between the request and response. Use them for parsing, validation, authentication, and error handling.

function logger(req, res, next) {
    console.log(`${req.method} ${req.url}`);
    next();
}

app.use(logger);

HTTP Methods

• GET: Retrieve data
• POST: Create data
• PUT/PATCH: Update data
• DELETE: Remove data

app.delete('/posts/:id', (req, res) => {
    res.json({ message: `Post with id ${req.params.id} deleted` });
});

JSON Responses

JSON is the standard format for data exchange.

app.get('/post', (req, res) => {
    res.json({ id: 1, title: 'Hello World' });
});

Environment Variables

Configure your project securely using environment variables.

.env file:

PORT=4000
DB_PASSWORD=supersecret

Usage in code:

require('dotenv').config();
const port = process.env.PORT || 3000;

Error Handling

Handle errors gracefully with middleware.

app.use((err, req, res, next) => {
    console.error(err.stack);
    res.status(500).json({ error: 'Something went wrong' });
});

Create Your First Express Project

1. Install Node.js and verify with node -v and npm -v.

2. Initialize your project:

mkdir my-first-express
cd my-first-express
npm init -y

3. Install Express:

npm install express

4. Create index.js:

const express = require('express');
const app = express();
const port = process.env.PORT || 3000;

app.get('/', (req, res) => {
    res.send('Hello from Express!');
});

app.listen(port, () => {
    console.log(`Server running at http://localhost:${port}`);
});

5. Run the server:

node index.js

6. Visit http://localhost:3000 to see your Express app in action.

Initial Best Practices

• Organize folders (routes/, controllers/, services/)
• Use middlewares for validation and authentication
• Handle errors with try/catch and error middleware
• Start with unit testing (jest, mocha)
• Add TypeScript when comfortable

Conclusion

Express is a great starting point for backend development with Node.js. It’s lightweight, simple, and teaches you the fundamentals of web servers. Once you master Express, you’ll be ready for more advanced frameworks like NestJS or AdonisJS.