Express JS Express Middleware

Question 1

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

Accepted Answer

req, res, next

Answer

Standard Express middleware receives the request object (req), response object (res), and the next() function.

Question 2

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

Accepted Answer

express.json()

Answer

express.json() is the built-in middleware that parses incoming requests with JSON payloads.

Question 3

What does express.static() middleware do?

Accepted Answer

Serves static files from a specified directory

Answer

express.static() serves static assets like HTML, CSS, images, and JS from a given root directory.

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

Calling app.use() without a path argument applies the middleware to every incoming request.

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

router.use() scopes middleware to only the routes handled by that specific router instance.

Express JS Practice Test