Clean Hooks

Hooks should make stateful behavior explicit. Effects are for synchronization with systems outside React, not for deriving ordinary render data.

R4: Effects

Use useEffect for:

• Subscriptions and cleanup
• Browser APIs and imperative widgets
• Network calls when the project does not use a data-fetching library
• Synchronizing React state with an external system

Do not use useEffect for values that can be computed during render.

// Bad - derived state via effect
const [fullName, setFullName] = useState("");