Using Express Router for Modularization

A router is a small group of routes and middleware that has no server of its own. You build it in a separate file, and then you attach it to the application at a path such as /books. Express creates one with express.Router(), and the application treats the whole group as a single piece of middleware.

This chapter builds a small bookstore API with routers. It covers how to split routes into router files, how to read data from the URL with route and query parameters, how to group and version those routers, and how to handle errors inside routes.