Express JS Express Middleware 2

Question 1

Which built-in Express middleware parses URL-encoded form data?

Accepted Answer

express.urlencoded()

Answer

express.urlencoded() parses incoming requests with URL-encoded payloads, such as HTML form submissions.

Question 2

What is the signature of an Express error-handling middleware?

Accepted Answer

(err, req, res, next)

Answer

Error-handling middleware must declare exactly four parameters: err, req, res, and next, in that order.

Question 3

Which popular third-party middleware is used for logging HTTP requests in Express?

Accepted Answer

morgan

Answer

morgan is the most widely used Express HTTP request logger middleware.

Question 4

What does the 'cors' middleware package primarily do in an Express app?

Accepted Answer

Enables Cross-Origin Resource Sharing by setting appropriate HTTP headers

Answer

The cors middleware sets headers like Access-Control-Allow-Origin to allow or restrict cross-origin requests.

Question 5

How do you invoke the next error-handling middleware from a route by passing an error?

Accepted Answer

next(err) with an error object or string

Answer

Calling next() with any argument (except 'route' or 'router') triggers the error-handling middleware chain.

Express JS Practice Test