React Senior Engineer Assessment

Q: What is this reactjs mock test?

This is a comprehensive reactjs mock test with 15 questions covering Architecture, Performance, Core Concepts. It simulates real technical interviews with timed conditions and provides detailed explanations.

Q: How long does the test take?

The test has a time limit of 75 minutes. You can pause and resume, but we recommend completing it in one sitting.

Q: Will I get feedback on my answers?

Yes! After each question, you receive immediate feedback with detailed explanations. At the end, you get a comprehensive report showing your strengths and areas for improvement.

Q: Is this test suitable for FAANG interview preparation?

Absolutely! Our questions are curated by FAANG interviewers and cover the exact topics and difficulty levels you'll encounter in top tech company interviews.

Question 1

How does React Fiber change the reconciliation process compared to the old stack reconciler?

Answer

It enables incremental rendering by breaking work into units called 'fibers'

Question 2

What is the primary difference between `useMemo` and `useCallback`?

Answer

useMemo returns a memoized value, useCallback returns a memoized function

Question 3

When implementing a 'Portal' in React, what happens to event bubbling?

Answer

Events bubble through the React component tree (virtual tree)

Question 4

What is the purpose of the `useId` hook introduced in React 18?

Answer

To generate unique IDs that are stable across server and client

Question 5

In a Redux toolkit setup, what is the 'ExtraReducers' field used for?

Answer

Handling actions defined outside of the slice (e.g., async thunks)

Question 6

Which method is the modern replacement for `componentDidCatch` in functional components?

Answer

There is currently no Hook equivalent; use a Class ErrorBoundary

Question 7

What does the `startTransition` API do in React 18?

Answer

It marks an update as non-urgent, allowing urgent updates to interrupt it

Question 8

How can you prevent a component from re-rendering when a Context value it doesn't use changes?

Answer

All of the above

Question 9

What is the 'Double Buffer' technique in React Fiber?

Answer

Using a 'current' tree and a 'workInProgress' tree to prepare updates

Question 10

Which Hook should be used if you need to read the layout from the DOM and synchronously re-render?

Answer

useLayoutEffect

React Senior Engineer Assessment

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