Interview Questions Answer

1. Discuss the advantages and limitations of React.

Answer:

Advantages:

• Fast performance due to Virtual DOM
• Reusable components
• Declarative approach for UI creation
• Large community and ecosystem

Limitations:

• Complexity for large-scale applications (state management)
• Potential learning curve for JSX and component-based structure

2. Explain Higher-Order Components (HOCs) in React.

Answer:

HOCs are a technique for sharing common component logic. They are functions that accept a component and return a new component with added functionality. This promotes code reuse and avoids code duplication.

3. What are some popular React state management libraries?

Answer:

For complex applications with a lot of shared state, libraries like:

• Redux: Centralized state container with predictable data flow.
• Context API: Built-in React feature for sharing data across components without prop drilling.

4. Explain strategies for optimizing performance in React applications.

Answer:

Here are some techniques to optimize React app performance:

• React.memo for Memoization: Caches component results to avoid unnecessary re-renders.
• Avoiding Unnecessary Re-renders: Use techniques like shouldComponentUpdate or PureComponent for class components to optimize re-renders based on prop/state changes.
• Code Splitting: Break down your codebase into smaller bundles for faster initial load times.

5. How would you handle API calls in a React application?

Answer:

There are various approaches for handling API calls in React:

• Fetch API: Built-in browser API for making HTTP requests.
• Axios: Popular library offering a simpler syntax and promise-based approach.
• State Management Libraries (Redux, Context API): For complex data management and centralized state handling.

6. Differentiate between state and props in React.

Answer:

• Props: Read-only values passed down from parent to child components. They provide data without modifying the child's internal state.
• State: Internal data managed by a component. It can be changed (using setState) to trigger re-renders of the component and its children.

7. Explain JSX and its role in React.

Answer:

JSX (JavaScript XML) is a syntax extension that lets you write HTML-like structures within your JavaScript code. It improves readability but is optional (you can use plain JavaScript for UI creation).

8. What are React components and their types?

Answer:

React components are reusable UI building blocks. They can be:

• Functional Components: Written as JavaScript functions that return JSX (describing the UI).
• Class-based Components: Defined using ES6 classes, allowing more complex logic and lifecycle methods.

9. Explain the concept of Virtual DOM in React?

Answer:

The Virtual DOM is a key concept in React. It's a lightweight copy of the actual DOM, and React uses it to improve performance by minimizing direct manipulations to the real DOM. Instead, React makes changes to the Virtual DOM, performs a "diffing" process to identify changes, and then updates only the necessary parts of the actual DOM. Candidates should understand the efficiency gains and benefits of using the Virtual DOM.

10. What is React and how does it differ from other JavaScript frameworks/libraries?

Answer:

This question assesses the candidate's understanding of React's fundamental concepts. The candidate should mention that React is a JavaScript library for building user interfaces, developed and maintained by Facebook. Emphasize the component-based architecture, virtual DOM, and the unidirectional data flow.