React Cleanup in useEffect MCQ Cleanup Practice Questions

Direction: Choose the correct option

How do you perform cleanup in useEffect?

A. By using useCleanup hook

B. By calling a cleanup function manually

C. By passing a second argument

D. By returning a function from the effect

Direction: Choose the correct option

When is the cleanup function called?

A. Never

B. Only when the component unmounts

C. After every render

D. Before the effect runs again (on next render) and on unmount

Direction: Choose the correct option

Which scenario typically requires cleanup?

A. Updating state

B. Fetching data

C. Setting up a subscription or timer

D. Rendering JSX

Direction: Choose the correct option

What will the following code do? useEffect(() => { const timer = setInterval(() => {}, 1000); return () => clearInterval(timer); }, []);

A. Set an interval that is cleared on unmount

B. Set an interval that runs forever

C. Set an interval that clears after each render

D. Cause an error

Direction: Choose the correct option

If an effect has no cleanup function, what happens?

A. The component may crash

B. It's a syntax error

C. No cleanup is performed

D. React adds a default cleanup

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