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 should you use Context instead of prop drilling or a state management library?

   Pass props when only a few levels need the data. Use Context for values many components read but that change rarely, such as theme, language or the logged-in user. Reach for a state library when shared state is large, updates often, or needs tools like selectors and devtools.

   IntermediateIn-depth3 min read
3. When should you use useEffect, and when should you avoid it?

   Use useEffect to sync your component with something outside React, such as a network request, a subscription or a browser API. Avoid it for work you can do during rendering or inside an event handler.

   IntermediateIn-depth2 min read