Express Router

Summary

Express's `Router` class lets you group related routes into their own modular, mountable mini-applications — essential for keeping a growing API organized.

• 1Split your routes into separate router files by resource (users, posts, orders).
• 2Mount each router under its own base path, e.g. `/api/users`.
• 3Apply router-level middleware (e.g. auth) that only affects routes in that router.