React Js Interview Questions

If you are preparing for a React js interview, it’s important to review some common interview questions and their answers. Below are some frequently asked React js interview questions along with their respective answers:

1. What is React js?

React is a popular JavaScript library for building user interfaces. It allows developers to create reusable UI components and efficiently update the DOM. React is maintained by Facebook and a community of individual developers and companies.

2. What are the key features of React js?

React js has several key features including:

• Virtual DOM for improved performance
• Component-based architecture for reusability
• JSX syntax for writing HTML in JavaScript
• Unidirectional data flow with Flux or Redux for state management

3. What is JSX and why is it used in React?

JSX is a syntax extension for JavaScript that allows developers to write HTML-like code within their JavaScript files. It’s used in React to make writing and understanding the UI components easier. JSX gets transpiled to regular JavaScript before it’s rendered in the browser.

4. What is the difference between state and props in React?

State is a built-in feature in React that represents the internal state of a component. It can be changed over time in response to user actions or network responses. Props, on the other hand, are inputs to a component that are passed in from its parent component. They are immutable and are used to pass data from parent to child components.

5. What is the purpose of key in React’s list rendering?

The key attribute is used in React’s list rendering to help identify which items have changed, been added, or been removed. It’s important to include keys when rendering dynamic lists to help React efficiently update the DOM without re-rendering the entire list.

6. Explain the concept of virtual DOM in React.

The virtual DOM is a lightweight copy of the actual DOM. When a component’s state changes, React compares the virtual DOM with the actual DOM and only updates the specific parts of the DOM that have changed. This process helps improve performance and makes React applications faster.

Conclusion

These are just a few of the many possible React js interview questions you may encounter. It’s important to thoroughly understand the fundamental concepts and features of React in order to confidently answer interview questions. Good luck with your React js interview preparation!