Careeroza
Common Mistakes
Pitfalls
- Missing dependencies: the effect uses a stale value. Add every value it uses to the array (ESLint warns you).
- Infinite loop: setting state in an effect with no dependency array, or depending on an object created each render.
- Using effects for calculations: derive values during render instead (
const total = items.length). - Runs twice in development: StrictMode mounts, unmounts and mounts again to test your cleanup. Production runs once.