🔀 Router-Level Middleware in Express JS | Beginner-Friendly Guide

💡 What Is Router-Level Middleware?

Router-level middleware works exactly like application-level middleware, but it is applied only to routes defined under a specific express.Router() instance.

This helps organize your project by grouping related routes and applying middleware only where needed.

Router-level middleware is attached to a specific router object instead of the entire Express application.

This means the middleware will run only for routes handled by that router.

Below is a complete example demonstrating router middleware, router routes, and prefix usage.

• 🔀 express.Router() creates a mini Express instance for grouping routes.
• ⚙️ router.use() applies middleware to all routes in this router.
• 🧭 The router is used with a prefix using app.use('/test', router).
• 📌 Now all routes inside this router become:
  • /test/
  • /test/about
• 📝 Middleware runs only for routes starting with /test.