What does `useMemo` do and when should you use it?

Summary

useMemo caches the result of a pure calculation between renders while its dependencies stay the same.

Longer Answer

Use it for expensive calculations, stable derived objects passed to memoized children, or dependency values that should not change identity unless inputs change. It runs during render, so the function must be pure.

Do not use useMemo everywhere. It is a performance optimization, not a semantic guarantee, and the dependency list must include every reactive value used by the calculation.

Key Points

• Use it for expensive calculations, stable derived objects passed to memoized children, or dependency values that should not change identity unless inputs change
• It runs during render, so the function must be pure
• Do not use useMemo everywhere
• For 'What does useMemo do and when should you use it?', the key is to explain what problem the concept solves, where it fits in React's rendering model, and what mistake causes production bugs.

Do not use useMemo everywhere. It is a performance optimization, not a semantic guarantee, and the dependency list must include every reactive value used by the calculation

Comparison / Tradeoffs

Do not use useMemo everywhere. It is a performance optimization, not a semantic guarantee, and the dependency list must include every reactive value used by the calculation. |

Summary

useMemo caches the result of a pure calculation between renders while its dependencies stay the same.

Longer Answer

For 'What does useMemo do and when should you use it?', the key is to explain what problem the concept solves, where it fits in React's rendering model, and what mistake causes production bugs.

Do not use useMemo everywhere. It is a performance optimization, not a semantic guarantee, and the dependency list must include every reactive value used by the calculation.

Key Points

• For 'What does useMemo do and when should you use it?', the key is to explain what problem the concept solves, where it fits in React's rendering model, and what mistake causes production bugs
• Do not use useMemo everywhere
• It is a performance optimization, not a semantic guarantee, and the dependency list must include every reactive value used by the calculation
• Use the answer to connect the concept back to a realistic production or interview scenario for 'What does useMemo do and when should you use it?'

Comparison / Tradeoffs