Recall the function signature of an Express middleware, i.e.,
(req, res, next). You might recognize this signature as being the very same that we’ve used for Express routes in the past. Well there’s a perfectly good reason for that: Express routes are middleware. Every route created in Express is also a middleware function handling the request and response objects at that part of the stack. Express routes also have the option of sending a response body and status code and closing the connection. These two features are a byproduct of Express routes being middleware, because all Express middleware functions have access to the request, the response, and the next middleware in the stack.
Move on when you’re ready.