Node.js · Express Concepts · Fresh / Intern · Concept
What is Express middleware and how does the chain work?
Short Interview Answer
Functions (req, res, next) that run in order; next() continues, next(err) jumps to error handlers.
Detailed Explanation
Order matters: parsers before routes, auth before protected routes, error handlers last. Forgetting next() hangs requests.
Common Mistake
Async middleware without catching rejections / calling next(err).