What are the advantages of Custom Hooks?

Functions that don’t call Hooks don’t need to be Hooks.

Wrapping Effects in custom Hooks is often beneficial because:

1
Code sharing: It allows sharing effects between components.
2
More declarative: It lets our components focus on the intent rather than the exact implementation of our Effects.
3
Code Quality: It makes the data flow to and from your Effects very explicit.
4
When React adds new features, we can remove those Effects without changing any of our components.

Difficulty: 5/10

Topics: code reuse, state encapsulation, abstraction

0-2 years experience

1
You need to fetch the current user's profile in two separate components. How would you use a custom hook to avoid duplicating the fetch logic?
2
If you move form field handling into a custom hook, what happens to the component's state and its re‑render behavior?
3
Suppose the custom hook you wrote should accept a URL parameter to fetch different resources. How would you design that API?

2-5 years experience

1
We have a component that uses a custom hook for a debounced search, and after a recent refactor the search no longer triggers. How would you debug the problem?
2
When choosing between a custom hook and a higher‑order component for sharing logic, what trade‑offs do you consider?
3
Explain how you would structure a custom hook that manages a WebSocket connection used by multiple components, and why that design is beneficial.

5-8 years experience

1
Our dashboard renders hundreds of widgets, each using a custom hook for data polling, and we’re seeing performance degradation. How would you evaluate and improve the hook’s design?
2
Describe how you would enforce consistent error handling and loading states across the app using a shared custom hook, and what architectural implications that brings.
3
If a custom hook’s useEffect depends on an object prop, what pitfalls could arise at scale and how would you mitigate them?

8+ years experience

1
We plan to migrate a large legacy codebase to use custom hooks for all side‑effects. What rollout strategy would you propose to coordinate across multiple teams while minimizing risk?
2
Discuss the long‑term maintenance considerations of exposing a library of custom hooks as a shared package across several products. How would you handle versioning and deprecation?
3
How would you design a custom‑hook framework that lets teams plug in their own implementations (e.g., analytics) without breaking existing components?