Technologies Coding Problems Bookmarks Learning Paths

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Implement useDebounce hook. | Custom Hooks | react Interview Questions | NextRound.in

Questions

3 of 14

1Implement useMediaQuery hook.

3Implement useDebounce hook.

4Implement useLocalStorage hook.

5List potential pitfalls or risks of Custom Hooks.

6What should we do in cleanup functions?

7What are the advantages of cleaning up after an effect?

8What should be returned by custom hooks?

9What is the useEffect cleanup function?

10What are the advantages of Custom Hooks?

11What should not be put into custom hooks?

12What points to note and take care of while writing custom hooks?

13When should we use a custom hook?

14Why do we need custom hooks?

react

State and Props

Class Components

Function Components

Lifecycle functions

Performance Optimisation

03 / 14

Implement useDebounce hook.

Difficulty: 5/10

debounce logic, custom hooks, performance optimization

javascript

Scenario Questions

0-2 years experience

1Can you walk me through how you'd implement a useDebounce hook that takes a value and a delay and returns the debounced value?
2If the component using your hook unmounts before the timeout fires, what cleanup step is required?
3What happens to the debounced output if the delay prop changes between renders?

2-5 years experience

1

Follow-up Questions

What could go wrong if you forget to clear the timeout in the cleanup function?
How would you write a unit test to verify the debounce timing behavior?
If the delay prop changes frequently, how does that affect the hook's behavior?

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You have a search input that triggers an API call on every keystroke. How would you integrate your useDebounce hook to reduce network traffic, and what edge cases would you watch for?

2During a code review, a teammate notes that your hook's effect runs on every render. How would you modify the implementation to avoid unnecessary re‑executions?

3If the API call fails, how do you ensure the debounced value still reflects the latest user input?

5-8 years experience

1In a dashboard with dozens of widgets each using useDebounce, how would you assess the overall performance impact and mitigate any slowdown?
2How would you adapt your hook to work correctly with server‑side rendering where setTimeout isn't available?
3If you needed a single hook that could handle both debounce and throttle behavior, how would you design its API and internal logic?

8+ years experience

1Your team is migrating legacy class components that implement manual debouncing to a shared functional library using useDebounce across many products. What architectural plan would you propose to ensure consistency and avoid regressions?
2How would you version, document, and deprecate this custom hook in a company‑wide component library to support future changes without breaking downstream applications?
3If the organization wants to enforce that all network requests are debounced, how would you embed useDebounce at an architectural level—perhaps via a higher‑order fetch wrapper—and what trade‑offs would you consider?