Svelte · Senior · Question 65 of 75

Why is mutating `data` received from `load` in a page component a bad idea?

✓Correct answer: It's owned by SvelteKit and will be replaced on the next navigation or invalidation; derive local state or call an action/invalidate instead
2It's read-only and throws in production
3It triggers a full page reload

Explanation

Treat data like props: compute with $derived, and use writable deriveds for optimistic UI.

Further reading

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