Technical Interview Questions for React Developer
1. What is React?
Answer: React is a JavaScript library used to build fast and interactive user interfaces.
2. What are the main features of React?
Answer: React provides reusable components, virtual DOM, JSX, and efficient state management.
3. What is JSX in React?
Answer: JSX is a syntax extension that allows writing HTML-like code inside JavaScript.
4. What are React components?
Answer: Components are reusable building blocks that define the structure and behavior of a UI.
5. What is the difference between functional and class components?
Answer: Functional components use functions and hooks, while class components use lifecycle methods.
6. What is the Virtual DOM?
Answer: Virtual DOM is a lightweight copy of the real DOM that improves application performance.
7. What are props in React?
Answer: Props are read-only data passed from a parent component to a child component.
8. What is state in React?
Answer: State stores dynamic data that can change during the component lifecycle.
9. What is the difference between props and state?
Answer: Props are passed from parent components, while state is managed inside a component.
10. What are React Hooks?
Answer: Hooks are functions that allow functional components to use state and lifecycle features.
11. What is useState in React?
Answer: useState is a hook used to create and update component state.
12. What is useEffect in React?
Answer: useEffect is a hook used to perform side effects like API calls and subscriptions.
13. What is the use of useMemo in React?
Answer: useMemo optimizes performance by memoizing expensive calculations.
14. What is the use of useCallback in React?
Answer: useCallback prevents unnecessary function recreation during component rendering.
15. What is React Router?
Answer: React Router is a library used for navigation and routing in React applications.
16. What is Redux?
Answer: Redux is a state management library used to manage application-wide data.
17. What is the difference between controlled and uncontrolled components?
Answer: Controlled components use React state, while uncontrolled components use the DOM directly.
18. What is component lifecycle in React?
Answer: Lifecycle describes the stages of component creation, updating, and removal.
19. What are keys in React?
Answer: Keys are unique identifiers used by React to efficiently update lists.
20. What is conditional rendering in React?
Answer: Conditional rendering displays UI elements based on certain conditions.
21. What is React Context API?
Answer: Context API allows sharing data between components without passing props manually.
22. What is lazy loading in React?
Answer: Lazy loading loads components only when they are needed to improve performance.
23. What is code splitting in React?
Answer: Code splitting divides application code into smaller bundles for faster loading.
24. How do you optimize React application performance?
Answer: Performance can be improved using memoization, lazy loading, optimized rendering, and efficient state management.
25. What is the difference between React and Angular?
Answer: React is a UI library focused on components, while Angular is a complete frontend framework.