What does middleware and app.use actually mean in Expressjs?

Question

Almost every Express app I see has an app.use statement for middleware but I haven\'t found a clear, concise explanation of what middleware actually is and what

Answer 1

Middlewares are functions executed in the middle after the input/source then produces an output which could be the final output or could be used by the next middleware until the cycle is complete.

It is like a product that goes through an assembly line where it gets modified as it moves along until it gets completed, evaluated or gets rejected.

A middleware expects some value to work on (i.e. parameter values) and based on some logic the middleware will call or not call the next middleware or send a response back to the client.

If you can't still grasp the middleware concept, it is in a way similar to the Decorator or Chain of command patterns.