Error response formatting in Express - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of formatting error responses in Express?

Formatting error responses helps clients understand what went wrong by providing clear, consistent messages and status codes.

beginner

Which HTTP status code is commonly used for a generic server error in Express?

The status code 500 is used for internal server errors indicating something went wrong on the server side.

beginner

How can you send a JSON error response with a message and status code in Express?

Use res.status(code).json({ error: 'message' }) to send a JSON error with the right HTTP status.

intermediate

Why should error responses include both a status code and a message?

Status codes tell the client the type of error, while messages explain details, making debugging easier.

intermediate

What is a common pattern to handle errors globally in an Express app?

Use an error-handling middleware function with four arguments (err, req, res, next) to catch and format errors consistently.

Which method sets the HTTP status code in an Express response?

A res.status()

B res.sendStatus()

C res.json()

D res.setStatus()

res.status() sets the HTTP status code before sending the response.

What is the correct way to send a JSON error message with status 404 in Express?

A res.sendStatus(404, { error: 'Not found' })

B res.json(404, { error: 'Not found' })

C res.status(404).json({ error: 'Not found' })

D res.error(404, 'Not found')

res.status(404).json({ error: 'Not found' }) sets status and sends JSON error.

In Express, what does an error-handling middleware function require?

A No parameters

B Four parameters: err, req, res, next

C Two parameters: req, res

D Three parameters: req, res, next

Error middleware must have four parameters to catch errors properly.

Why is it important to send consistent error response formats?

A To help clients parse and handle errors easily

B To make the server faster

C To reduce the size of responses

D To avoid using status codes

Consistent formats help clients understand and react to errors correctly.

Which status code indicates a client error due to bad input?

A 500

B 302

C 200

D 400

400 means Bad Request, indicating client-side input errors.

Explain how to create a global error handler in Express and why it is useful.

Think about middleware that catches errors and sends a response.

Describe the key parts of a well-formatted error response in an Express app.

What does the client need to understand the error?