react-useeffect

SKILL.md

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 |

來自官方文檔的 React useEffect 最佳實踐。在編寫/查看 useEffect、useState 以獲得派生值、數據獲取或狀態同步時使用。教導何時不使用 Effect 和更好的替代方案。 來源：fluid-tools/claude-skills。

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