21 React js Interview Questions and Answers

React js Interview Questions and Answers for experienced software developer

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The JavaScript tools are slowly and steadily firming their roots on the marketplace and the demand for React certification is exponentially increasing. It is becoming increasingly difficult to choose the appropriate technologies to create an application or website. React is considered by others to be the fastest-growing Javascript framework.

check all 21 questions here

1. Compare and contrast developing ES5 and ES2015 (also known as ES6) react components. What are the pros and cons of using one or the other? Include notes on default props, initial state, PropTypes and DisplayName.

2. Explain the Virtual DOM and how React renders it to the DOM?

3. Compare and contrast the different lifecycle methods used in the React Component. How might understanding these help build certain interfaces/features?

4. What is the difference between state and props?

5. How would you create Higher Order Components (HOCs) in React?

6. What is the significance of keys in React?

7. What is the use of refs in React?

8. What are pure functional Components?

9. How can React handle or restrict Props to some types, or require some Props to exist?

10. What is prop drilling and how can you avoid it?

11. What is the StrictMode component and why would you use it?

12. What is the important architectural difference between a JavaScript library like React and a JavaScript framework like Angular? Why does that impact the decision to use one or the other for a project?

13. If you required a component to perform an action only once the component was initially made, how would you do that with a class object? And how are you going to accomplish this with a function component?

14. What are the most common approaches to styling a React application?

15. If you were working on a React application that was rendering a page very slowly, how would you be investigating and fixing the issue?

16. What is useState() and useEffect() in React?

17. What is the difference between a controlled component and an uncontrolled component?

18. How are you going to differentiate Redux from Flux?

19. What is the use of render() function in ReactJS?

20. Explain Redux and its components?

21. Explain React.Fragment, React.lazy and Suspense?

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