Interview Q&A / React

1. What is the difference between useMemo and useCallback, and when should you not use them?

   useMemo caches the result of a calculation, and useCallback caches a function itself, both until their dependencies change. Use them for expensive calculations or to keep values stable for memoized children or effect dependencies; skip them for cheap work, where they only add complexity.

   IntermediateIn-depth3 min read
2. When is useMemo actually worth using?

   Use it when a calculation is measurably slow, or when you need a stable object or array reference to pass to a memoised child or a hook dependency. Wrapping cheap calculations adds overhead and noise.

   IntermediateQuick answer1 min read