react-useeffect

Effects are an escape hatch from React. They let you synchronize with external systems. If there is no external system involved, you shouldn't need an Effect.

| Derived state from props/state | useState + useEffect | Calculate during render | | Expensive calculations | useEffect to cache | useMemo | | Reset state on prop change | useEffect with setState | key prop | | User event responses | useEffect watching state | Event handler directly |

| Notify parent of changes | useEffect calling onChange | Call in event handler | | Fetch data | useEffect without cleanup | useEffect with cleanup OR framework |

公式ドキュメントからの React useEffect のベスト プラクティス。 useEffect、派生値の useState、データのフェッチ、または状態の同期を作成/レビューするときに使用します。エフェクトを使用してはいけない場合と、より良い代替案を教えます。 ソース: petekp/claude-code-setup。