How to Use Middleware in Node.js (Express) with Real-Time Example Middleware is one of the most powerful concepts in Express.js, allowing you to intercept and modify requests and responses. In this guide, we’ll explore middleware usage in Express — with a real-world use case: Authentication Middleware . 📌 What is Middleware? In Express.js, middleware is a function that sits between the request and response in the HTTP lifecycle. It has access to: req – the HTTP request object res – the HTTP response object next() – a function that passes control to the next middleware Think of middleware as the logic that can: Log request details Check if a user is authenticated Parse request bodies (JSON, form data, etc.) Serve static files Handle errors Middleware runs before the final route handler and can either: Terminate the request (by sending a response) Call next() to pass control to t...