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Are you preparing for a React.js interview? Here are some essential questions to test your knowledge:
1️⃣ What are React Hooks? Name a few commonly used ones.
2️⃣ How does React handle state management?
3️⃣ What is the difference between controlled and uncontrolled components?
4️⃣ Explain the Virtual DOM and how it improves performance.
5️⃣ How does React’s reconciliation process work?
6️⃣ What is the use of useMemo and useCallback?
7️⃣ How do you handle side effects in React?
8️⃣ What are React Fragments, and why use them?
9️⃣ How can you optimize performance in a React application?
🔟 What are higher-order components (HOCs), and where would you use them?
You Should Know:
1. React Hooks
React Hooks allow you to use state and other React features without writing a class. Commonly used hooks include:
– useState: Manages state in functional components.
– useEffect: Handles side effects like data fetching or subscriptions.
– useContext: Accesses context in functional components.
Example:
[javascript]
import React, { useState, useEffect } from ‘react’;
function Example() {
const [count, setCount] = useState(0);
useEffect(() => {
document.title = You clicked ${count} times;
});
return (
);
}
[/javascript]
2. Virtual DOM
The Virtual DOM is a lightweight copy of the actual DOM. React uses it to improve performance by minimizing direct DOM manipulations.
How it works:
- React creates a virtual representation of the UI.
- When state changes, React compares the new Virtual DOM with the previous one (diffing).
- Only the differences are updated in the actual DOM.
3. Optimizing Performance
- Use `React.memo` to prevent unnecessary re-renders.
- Use `useMemo` and `useCallback` to memoize expensive calculations and functions.
- Lazy load components using `React.lazy` and
Suspense.
Example:
[javascript]
const ExpensiveComponent = React.memo(({ compute, value }) => {
const result = compute(value);
return
;
});
[/javascript]
4. Higher-Order Components (HOCs)
HOCs are functions that take a component and return a new component with additional props or functionality.
Example:
[javascript]
function withLogger(WrappedComponent) {
return function(props) {
console.log(‘Rendered:’, WrappedComponent.name);
return
};
}
[/javascript]
What Undercode Say:
Mastering React requires a deep understanding of its core concepts like Hooks, Virtual DOM, and performance optimization techniques. Practice these concepts with real-world examples and commands to solidify your knowledge. For further reading, check out the official React documentation.
Commands to Practice:
- Use `npx create-react-app my-app` to set up a new React project.
- Run `npm start` to launch the development server.
- Use `npm test` to run tests in your React application.
By combining theoretical knowledge with hands-on practice, you’ll be well-prepared for any React interview. 🚀
References:
Reported By: Sumit Yadav – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
