juniorReact Hooks
What is dependency array in useEffect?
Updated May 6, 2026
Short answer
It controls when useEffect runs based on dependencies.
Deep explanation
React compares dependencies using shallow comparison to decide whether to re-run effects.
Real-world example
Re-fetching data when filter changes.
Common mistakes
- Missing dependencies causing stale values.
Follow-up questions
- What is shallow comparison?
- Can you pass empty array?