Express.js: From Beginner to Advanced

Express.js is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications.

In this guide, we'll cover everything from basic routing and middleware to advanced patterns like error handling, authentication, and production deployment.

Getting Started

First, install Express.js using npm: `npm install express`

Create your first Express server by calling `express()` and listening on a port. Express handles HTTP methods (GET, POST, PUT, DELETE) through clean, chainable route handlers.

Middleware

Middleware functions are functions that have access to the request object, response object, and the `next` function. They can execute any code, modify the req/res objects, end the request-response cycle, or call the next middleware.

Advanced Patterns

As your application grows, you'll want to use Router to organize routes, implement proper error handling with a global error handler, add authentication middleware using JWT, and structure your application with MVC patterns.