What are req and res in an Express handler?
PICTURE THIS: STACK VS QUEUE
Simple meaning
req is the incoming request: params, query, body, headers, and cookies.
WHY — Express instead of guessing?
Why interviewers care about Express:
who only read docs from people who shipped.
and tied to Full Stack work.
Name the idea, why it exists, then one short example.
End with when you use it and one common pitfall.
STEPS — What happens step by step?
Before you speak the answer, walk the interviewer through these steps:
- 1req is the incoming
request: params, query, body, headers, and cookies.
- 2res is the response
object you use to set status, headers, and send JSON or files.
- 3Most API bugs show
up first as unexpected values on req or the wrong payload on res.
- 4Give an example
One tiny concrete case you can say aloud.
- 5Common mistake
What juniors usually get wrong.
- 6Close
When you pick this over the alternative.
EXAMPLE — See it in action
Here's a short line you can speak, broken into clear beats:
Note: Adapt this scaffold to your own project — keep it under 60–90 seconds.
Key takeaway
req is the incoming request: params, query, body, headers, and cookies. res is the response object you use to set status, headers, and send JSON or files.