React Interview Questions

This is a very important guide for Beginner to Advanced React JS Interview QNA. These all questions are asked in real interviews via companies.

1. What are synthetic events?
2. How does React work?
3. What is the distinction between client-side and server-side rendering?
4. Why use React instead of other frameworks, like Angular, or VueJS?
5. What is reconciliation?
6. What is the Virtual DOM?
7. How to Optimize React App?
8. What is React Fiber?
9. What are React Portals?
10. What is useReducer in React?
11. What are Error Boundaries?
12. What is Profiler in React JS?
13. Why is there a need for using keys in lists?
14. What are the differences between controlled and uncontrolled components?
15.  What is prop drilling in React?
16. What are custom hooks? Create a hook.
17. Explain Strict Mode in React.
18. How do I pass data between Child to Parent react components?
19. Difference between a class Component and a Functional Component?
20. What are the hooks, you have used?
21. What is the purpose of useCallback?
22. What is the purpose of useMemo?
23. Explain Forwarding Refs in React.
24. What are Class-based lifecycle methods?
25. Implementing Debounce?
26. Implement Throttle?
27. How would you be able to achieve componentDidMount, componentDidUpdate, & componentDidUnMount in a functional-based component?
28. What are pure components and what is their purpose?
29. What are higher-order components?
30.  What HODs have you used? Write an example.
31. Have you used the context API? Explain it.
32. We already have state management in React, so why so for Redux?
33. How does Redux work?
34. Have you used any middleware?
35. What is the purpose of using middleware?
36. How to Write Unit Tests in React?
37. Explain the CORS error and how to fix it.
38. Explain the concept of “lifting up in React”.
39. How can we change props in React?
40. Is setState() method synchronous or asynchronous?
41. How to Handlers  Async Events in React?
42. Is setState() method synchronous or asynchronous?
43. What are Async Event Handlers in React?
44. Can we setState through the onClick event in React?
45. Latest version of React JS, What features in Latest React version?
46. What is the difference between Promises and Observables?
47. Explain the concept of “lifting up in React”