Middleware functions are functions that have access to the request object (req
), the response object (res
), and the next middleware function in the application’s request-response cycle. The next middleware function is commonly denoted by a variable named next
.
Middleware functions can perform the following tasks:
- Execute any code.
- Make changes to the request and the response objects.
- End the request-response cycle.
- Call the next middleware function in the stack.
If the current middleware function does not end the request-response cycle, it must call next()
to pass control to the next middleware function. Otherwise, the request will be left hanging.