Response helpers (json, error) in Svelte - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the json() helper do in SvelteKit?

The json() helper creates a response with JSON content and the correct Content-Type header. It formats data so the client can easily read it as JSON.

beginner

How do you use the error() helper in SvelteKit?

You call error(status, message) to create an error response with a status code and message. This stops the request and shows an error page or message.

intermediate

Why is it better to use json() instead of manually creating a JSON response?

Because json() automatically sets the right headers and formats the data correctly, making your code cleaner and less error-prone.

intermediate

What happens if you use error(404, 'Not found') in a SvelteKit load function?

The request stops and SvelteKit shows a 404 error page with the message 'Not found'. This helps handle missing data or pages gracefully.

beginner

Can you customize the error message shown to users when using error()?

Yes, you provide a custom message as the second argument to error(). This message can explain what went wrong in simple words.

What header does the json() helper automatically set?

A Content-Type: text/html

B Authorization: Bearer token

C Content-Type: application/json

D Cache-Control: no-cache

The json() helper sets the Content-Type header to application/json so the client knows the response is JSON.

What does error(500, 'Server error') do in SvelteKit?

A Returns a JSON response with status 200

B Throws a 500 error with message 'Server error'

C Redirects to the home page

D Logs the error but continues loading

The error() helper throws an error response with the given status and message, stopping the request.

Which helper should you use to send JSON data from a SvelteKit endpoint?

A fetch()

B error()

C redirect()

D json()

Use json() to send JSON data with proper headers from an endpoint.

If you want to stop a request and show a 404 page, which helper do you use?

A error(404, 'Not found')

B throw new Error('Not found')

C redirect('/404')

D json()

Using error(404, 'Not found') stops the request and shows the 404 error page.

What type of value does json() expect as input?

A A JavaScript object or array

B A string of HTML

C A number only

D A boolean value

json() expects a JavaScript object or array to convert into JSON format.

Explain how and why you would use the json() helper in a SvelteKit endpoint.

Think about sending data from server to client in a clean way.

Describe the purpose of the error() helper and how it affects the user experience in SvelteKit.

Consider what happens when something goes wrong on the server.