FrontendHaltReact·Intermediate·Coding·1 min read
Why is copying props into state with an effect often wrong?
Short interview answer
It creates two sources of truth and an extra render with temporarily stale derived state. Compute inexpensive values during render, memoize only costly pure computation when measured, or deliberately reset state through identity when the product requires it.
Example
// Anti-pattern: effect mirrors a prop into stateuseEffect(() => setFullName(`${first} ${last}`), [first, last]);
// Just derive during render:const fullName = `${first} ${last}`;Key takeaway
Explain the underlying mental model clearly, then support it with a concrete example and its trade-offs.