Express JS Express Middleware

Question 1

What are the three arguments a standard Express middleware function receives?

Accepted Answer

req, res, next

Answer

request, response, callback

Answer

req, res, err

Answer

req, next, done

Question 2

Which built-in Express middleware parses incoming JSON request bodies?

Accepted Answer

express.json()

Answer

express.bodyParser()

Answer

express.parseJSON()

Answer

express.body()

Question 3

What does express.static() middleware do?

Accepted Answer

Serves static files from a specified directory

Answer

Caches dynamic responses

Answer

Sets static headers

Answer

Compresses static assets

Question 4

What type of middleware runs for every route regardless of path or method?

Accepted Answer

Application-level middleware registered with app.use() without a path

Answer

Route-level middleware

Answer

Error-handling middleware

Answer

Third-party middleware

Question 5

How do you apply middleware only to a specific router in Express?

Accepted Answer

Register it with router.use() on that router instance

Answer

Pass it as the first argument to app.listen()

Answer

Use app.only()

Answer

Set middleware.scope = 'router'

Question 6

What happens if a middleware function does not call next() or send a response?

Accepted Answer

The request hangs and the client never receives a response

Answer

Express automatically sends a 200 OK

Answer

The next middleware runs anyway

Answer

Express throws an error