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Are you preparing for a React JS interview? If so, you might be wondering what are the most commonly asked questions in React JS interviews. In this article, we will discuss some of the top interview questions that you should be prepared to answer.

1. What is React JS?

React JS is a popular JavaScript library for building user interfaces. It allows developers to create reusable UI components and efficiently update the UI when data changes. React uses a virtual DOM to optimize performance, and it is often used in combination with other libraries and frameworks, such as Redux and GraphQL.

2. What are the key features of React JS?

Some of the key features of React JS include its component-based architecture, virtual DOM for efficient updates, JSX syntax for writing HTML in JavaScript, and the ability to create reusable UI components. React also has a strong ecosystem of third-party libraries and tools, making it a popular choice for building modern web applications.

3. What is JSX?

JSX is a syntax extension for JavaScript that allows developers to write HTML-like code within their JavaScript files. This can make the code more readable and maintainable, and it is a key feature of React JS. JSX is transpiled to standard JavaScript using tools like Babel, so that it can be understood by the browser.

4. What is virtual DOM and how does it work?

The virtual DOM is a representation of the actual DOM in memory. When changes are made to the UI, React first updates the virtual DOM and then compares it with the actual DOM to identify the minimal set of changes needed to update the UI. This helps to minimize the number of DOM manipulations and improve performance.

5. What are the differences between class components and functional components?

Class components are ES6 classes that extend from React.Component and have a render method, while functional components are simply JavaScript functions that return JSX. Functional components are simpler and easier to understand, and they have been favored in recent years due to the introduction of Hooks in React.

These are just a few of the many questions that you might encounter in a React JS interview. It’s important to be familiar with the fundamentals of React, as well as its ecosystem and best practices. Good luck with your interview preparation!