In today’s fast-paced tech landscape, React has emerged as one of the most popular JavaScript libraries for building user interfaces. As companies increasingly seek skilled React developers, the demand for comprehensive knowledge in this area has skyrocketed. Preparing for a React interview requires not only understanding the library’s concepts but also being familiar with common interview questions. In this article, we present a Top 100 React Interview Questions List to help you prepare effectively.

1. What is React?
2. Key Features of React
3. Basic Questions
4. Intermediate Questions
5. Advanced Questions
6. Hooks Questions
7. Performance and Optimization Questions
8. Testing and Debugging Questions
9. Miscellaneous Questions
10. Practical Questions
11. Behavioral Questions
12. Final Questions
13. Conclusion

What is React?

React is a JavaScript library created by Facebook for building user interfaces, particularly for single-page applications where a responsive and dynamic experience is essential. Its component-based architecture allows developers to create reusable UI components, making the development process more efficient.

Key Features of React

• Component-Based: React allows developers to break down complex UIs into smaller, reusable components.
• Virtual DOM: This optimizes rendering by keeping a lightweight representation of the actual DOM.
• Unidirectional Data Flow: Data flows in one direction, which makes it easier to understand and debug applications.
• Declarative UI: Developers can describe what their UI should look like, and React takes care of updating it when data changes.

Basic React Interview Questions

1. What is React?
2. What are the main features of React?
3. Explain the concept of JSX.
4. What are components in React?
5. Differentiate between functional and class components.
6. What is the purpose of render() in React?
7. What is the virtual DOM?
8. How does React handle the event system?
9. What are props in React?
10. How do you pass data from parent to child components?

Intermediate React Interview Questions

11. What is state in React?
12. Explain the lifecycle methods of a React component.
13. What is the difference between state and props?
14. How do you update the state in a class component?
15. What is the significance of key in React?
16. What are controlled and uncontrolled components?
17. Explain the concept of lifting state up.
18. What is the use of useEffect hook?
19. How do you handle forms in React?
20. What are higher-order components (HOCs)?

Advanced Questions

21. What is the purpose of useMemo and useCallback hooks?
22. Explain React Context API.
23. What are React fragments?
24. How can you optimize performance in a React application?
25. What is the purpose of React.StrictMode?
26. How do you implement code splitting in React?
27. What are render props?
28. How does error handling work in React?
29. Explain how to manage state with Redux.
30. What are the differences between Redux and Context API?

Hooks Questions

31. What are hooks in React?
32. Explain the useState hook.
33. How do you create a custom hook?
34. What is the useReducer hook, and when would you use it?
35. Explain the purpose of useRef hook.
36. What is the difference between useEffect and componentDidMount?
37. How does useLayoutEffect differ from useEffect?
38. What are side effects in React?
39. How can you use the useContext hook?
40. Explain the rules of hooks.

Performance and Optimization Questions

41. What is memoization, and how does it work in React?
42. What is the significance of React.memo()?
43. How can you prevent unnecessary re-renders in React?
44. Explain lazy loading in React.
45. What are the best practices for optimizing a React application?
46. How does the shouldComponentUpdate method work?
47. What is reconciliation in React?
48. How can you use web workers with React?
49. What are the trade-offs of server-side rendering (SSR)?
50. Explain the concept of static site generation (SSG).

Also Read: Best HTML Interview Questions for Freshers

Testing and Debugging Questions

51. How do you test React components?
52. What is the purpose of Jest in React?
53. How can you use React Testing Library?
54. Explain snapshot testing in React.
55. What tools do you use for debugging React applications?
56. How do you handle asynchronous code in tests?
57. What are some common performance bottlenecks in React?
58. How can you profile a React application?
59. What is end-to-end testing in the context of React?
60. How do you mock API calls in tests?

Miscellaneous React Interview Questions

61. What are the differences between React and Angular?
62. Explain the concept of a single-page application (SPA).
63. What are some common React design patterns?
64. How do you handle routing in React applications?
65. What is the purpose of React Router?
66. How do you manage API calls in a React application?
67. What is the purpose of the useDebugValue hook?
68. What are the benefits of using TypeScript with React?
69. Explain how to implement authentication in a React application.
70. What are the implications of using inline styles in React?

Practical Questions

71. How would you structure a large React application?
72. Can you demonstrate how to create a simple CRUD application in React?
73. How do you handle global state in a React application?
74. What is the process for integrating third-party libraries in React?
75. How would you implement lazy loading of images in a React app?
76. Can you demonstrate how to use the Context API?
77. How do you create a modal component in React?
78. How would you implement pagination in a React application?
79. What is the process for deploying a React application?
80. How can you use the Intersection Observer API in React?

Behavioral Questions

81. Describe a challenging problem you faced while working with React.
82. How do you stay updated with the latest React developments?
83. Describe a project where you used React.
84. How do you approach learning new technologies?
85. What is your experience with version control systems like Git?
86. How do you handle feedback and criticism in a team setting?
87. Can you describe a situation where you had to troubleshoot a bug in a React application?
88. How do you ensure code quality in your projects?
89. What tools do you prefer for project management?
90. How do you prioritize tasks when working on a project?

Final Questions

91. What do you like most about React?
92. How do you see the future of React evolving?
93. Can you explain the concept of progressive web apps (PWAs)?
94. How would you implement dark mode in a React application?
95. What are some common pitfalls to avoid when working with React?
96. How do you handle accessibility in React applications?
97. Explain the difference between client-side and server-side rendering.
98. What role does the React Developer Tools play in development?
99. How do you approach code reviews for React projects?
100. What are your thoughts on state management libraries other than Redux?

Conclusion

This comprehensive list should help you prepare effectively for a React interview, covering a wide range of topics. Remember to not only understand the answers but also to practice coding and real-world applications of the concepts. Good luck!