Run reusable logic in the request pipeline before the final route handler responds.
Middleware is one of the most important ideas in Express. A middleware function can inspect or modify a request, perform some work, and then call next() to pass control to the next middleware or route handler.
This makes middleware useful for tasks such as logging, authentication, validation, parsing request data, handling errors, and adding information to the request. Understanding the order in which middleware runs is especially important because it directly affects how an Express application behaves.
What you'll walk away knowing