Node.js Express.js & REST APIs 5

Question 1

What is the purpose of the helmet middleware in an Express REST API?

Accepted Answer

Setting secure HTTP headers to reduce common vulnerabilities

Answer

Helmet sets security-related HTTP headers like Content-Security-Policy and X-Frame-Options automatically.

Question 2

What happens if you call next() inside a route handler after already sending a response with res.json()?

Accepted Answer

The next middleware may run and trigger a headers-already-sent error

Answer

Calling next() after res.send() causes downstream middleware to run and risks 'Cannot set headers after they are sent' errors.

Question 3

Which approach correctly handles async errors in an Express route in Express 4?

Accepted Answer

Wrapping the handler in try/catch and calling next(err)

Answer

In Express 4 async handlers, try/catch with next(err) routes the error to Express error middleware since rejected promises are not caught automatically.

Question 4

What is content negotiation in the context of a REST API?

Accepted Answer

The server selecting the response format based on the client's Accept header

Answer

Content negotiation uses the client's Accept header to determine whether to respond with JSON, XML, or another format.

Question 5

Which Express response method streams a file to the client with automatic Content-Type detection?

Accepted Answer

res.sendFile()

Answer

res.sendFile() sends a file at a given absolute path, automatically setting Content-Type and handling streaming.

Node.js Practice Test

Node.js Practice Test

Node.js Express.js & REST APIs 5