Express.js Essentials: A Beginner's Guide

Author: Meenakshi Sundareswaran Ravichandran

As a popular Node.js web framework, Express.js simplifies building web applications and APIs. This beginner's guide covers key Express.js concepts every developer should know.

Routing Made Easy

Routing determines how an app responds to client requests. With Express.js, defining routes for different HTTP methods is straightforward:

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

Middleware Functions

Middlewares are functions executed during the request-response cycle. They can perform tasks like logging, parsing request bodies, and more:

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

Handling Requests and Responses

The req and res objects represent the HTTP request and response. Access and modify them to handle requests and send responses in Express.js:

app.get('/users/:id', (req, res) => {
  const userId = req.params.id;
  res.json({ userId });
});        

Managing Sessions and Cookies

Express.js relies on third-party middlewares like express-session and cookie-parser for session and cookie management:

app.use(session({ secret: 'your-secret-key' }));

app.get('/set-session', (req, res) => {
  req.session.user = { id: 1 };
  res.send('Session set');
});        

Working with Headers

Access and modify HTTP headers using req.headers and res.headers in Express.js:

app.get('/headers', (req, res) => {
  const userAgent = req.headers['user-agent'];
  res.set('X-Custom-Header', 'Hello, World!');
  res.send(`User-Agent: ${userAgent}`);
});        

Logging Made Simple

Use third-party loggers like morgan for logging in Express.js:

app.use(morgan('combined'));        

Rendering Dynamic Views

Express.js supports templating engines like ejs for rendering dynamic views:

app.set('view engine', 'ejs');

app.get('/users', (req, res) => {
  const users = [{ id: 1, name: 'John' }];
  res.render('users', { users });
});        

By mastering these concepts, developers can build robust web apps and APIs using Express.js. Start your journey today!

Reference: https://expressjs.com/

Reference For MongoDB Performance Optimization: https://www.dhirubhai.net/feed/update/urn:li:activity:7171010279919480833