Introduction

React or React Js is one of the most popular Javascript front-end libraries with a strong foundation and a large community.

It is one of the most flexible Javascript libraries for building reusable UI components. React Js is a declarative and efficient open-source, component-based front-end library that creates the application’s view layer. Facebook developed it and is now used in applications like Whatsapp and Instagram.

The main objective of React is to develop a User Interface (UI) that improves the speed of the applications. It uses the virtual DOM that enhances the speed of the applications.

React Js can also be used on the client-side, server-side, and other frameworks. 

This article lists all the common React Js interview questions from basic to advanced levels.

Basic Level Interview Questions

1. What is React?
2. What are the various advantages of using React?
3. List some of the limitations of using React.
4. Which one is used by React- HTML or JSX?
5. Explain the concept of flux in React.
6. Define action in Redux.
7. What is Jset?
8. Explain dispatcher.
9. What do you understand about the call-back function? Explain its purpose.
10. Define the term high order component.
11. Explain useState() in React?
12. What are the keys to React?
13. Explain Javascript XML.
14. Explain the key differences between functional and class components.
15. What is virtual DOM?
16. What is the main motive for introducing DOM?
17. Explain the process of using virtual DOM to render the UI.
18. Differentiate between controlled and uncontrolled components?
19. Explain props in React.
20. Define React state.
21. Write the syntax of declaring a state object.
22. Explain the various types of side effects that occur in React component.
23. Explain prop drilling in React.
24. Define the error boundary, and at what places does the error boundary detect an error?
25. Explain React Hooks.
26. Why were Hooks introduced in React?
27. What basic rules need to be followed while using React Hooks?
28. Explain the use of use effect React Hooks.
29. What is the reason for using refs by React Hooks?
30. Explain Custom Hooks.
31. Is it possible to use the Custom hooks inside the classes?
32. Name the two arguments that are accepted by the use effect React.
33. Define the Presentational segment.
34. Highlight the use of the super keyword in React.
35. How will you achieve server-side rendering in React?
36. Compare the get initial state() and constructor()?
37. How will you dispatch the data in-store?
38. How will you do the task of spilling the reducers?
39. Name the five predefined prototypes used in React.
40. Explain the purpose of using blindActionsCreators.
41. Is there any difference lying in the syntax of ES6 and ES5?
42. Is it necessary to start component names with a capital letter?
43. Explain how fragments are better than container divs.
44. What is the use of the switch keyword in React Router v4?
45. What do you know about the term Babel?

Interview Questions for Experienced

1. Elaborate Strict Mode tool in React?
2. Highlight the various issues that StrictMode solves.
3. How will you prevent re-renders in React?
4. What are the different ways to style a React component?
5. Explain the various techniques that are meant to optimize the React app performance.
6. How can we pass the data between react components?
7. Explain Higher Order Components.
8. Explain different phases of the component lifecycle.
9. Name the various lifecycle methods of React.
10. What does static typing refer to?
11. Does React Hook work with static typing?
12. Define the types of Hooks in React.
13. Differentiate between React Hooks and Classes?
14. Explain how Hooks are a better option in comparison with the classes.
15. Do Hooks cover all the functionalities offered by classes?
16. Explain React Router.
17. Can we consider React Hook as a replacement tool for Redux?
18. Define conditional rendering in React.
19. Write a program that creates simple React Hooks.
20. What is the use of npm and npx command-line tools?
21. Elucidate the term switching component.
22. Is it possible to re-render the view when the browser is resized?
23. How will you pass the data between sibling components using React router?
24. How will you perform automatic redirect after login?
25. Is it possible to create a switching component for displaying different pages?
26. What is a yield catchphrase in JavaScript?
27. Describe a synthetic event in React Js.
28. What is the process of updating the state in React?
29. Explain the use of the arrow function in React.
30. Define ‘create-react-app’?
31. What is the children’s prop?
32. Define error boundaries.
33. For what purpose empty tags <> </> are used?
34. Define strict mode.
35. Explain reacted portals.
36. What is the context?
37. Explain the use of Webpack.
38. Explain Babel in React Js.
39. Highlight the major issue that occurs while using MVC architecture in React.
40. What to do when there is more than one line expression?
41. Define reduction.
42. Define the term synthetic events.
43. How and when to use the top-class elements for the function element?
44. How will you share an element in the parsing?
45. Define the term reconciliation.
46. Define the term ‘Restructuring.’
47. Explain the terms Mounting and Demounting.
48. What do you mean by the term Fragments?
49. Explain the difference between createElement and cloneElement.
50. Name the important methods of the react-dom package.

React Styling Interview Questions

1. What is the use of styles in React?
2. What are the different ways in which we can style the React components?
3. Explain the CSS Module of styling.
4. Explain Styled components.
5. Define the term ‘Painless Maintenance’.