Individual skill
react-useeffect
React useEffect best practices from official docs. Use when writing/reviewing useEffect, useState for derived values, data fetching, or state synchronization. Teaches when NOT to use Effect and better alternatives.
skills-imported/react-useeffect/SKILL.md
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# You Might Not Need an Effect
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.
## Quick Reference
| Situation | DON'T | DO |
|-----------|-------|-----|
| 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 |