List of most commonly asked React Interview Questions.

1. What is React and What are its key features?

React is an open-source JavaScript library used for building user interfaces (UIs) and single-page applications. It was developed by Facebook and has gained widespread adoption in the web development community. React follows a component-based architecture, allowing developers to build reusable UI components and efficiently update and render them when the underlying data changes.

Key Features of React:

1. Component-Based Architecture: React encourages building UIs as a composition of reusable components. Components encapsulate their own logic and state, making it easier to develop and maintain complex UIs.

2. Virtual DOM: React utilizes a virtual representation of the actual DOM, known as the virtual DOM. It creates a lightweight copy of the DOM and performs efficient diffing algorithms to update only the necessary parts of the actual DOM, minimizing the number of real DOM manipulations and enhancing performance.

3. Declarative Syntax: React uses a declarative syntax, allowing developers to describe how the UI should look based on the current application state. Developers can focus on describing the desired UI outcome, and React handles the underlying updates efficiently.

4. JSX: React introduces JSX (JavaScript XML), which is an extension to JavaScript that allows developers to write HTML-like code within JavaScript. JSX simplifies the process of building React components by providing a familiar HTML-like syntax.

5. React Router: React Router is a popular routing library that allows developers to handle client-side routing in React applications. It enables the creation of multiple routes and navigation within a single-page application.

6. State Management: React provides a mechanism to manage component-level state using the useState hook or state management libraries like Redux or MobX. This allows developers to handle dynamic data and keep the UI in sync with the application state.

7. Reusability and Composability: React components promote reusability and composability, enabling developers to build modular UIs. Components can be reused across different parts of an application, reducing code duplication and enhancing maintainability.

8. Community and Ecosystem: React has a vibrant and active community that contributes to its ecosystem. There are numerous third-party libraries, tools, and extensions available, providing solutions for various aspects of web development with React.

These key features of React make it a powerful and popular choice for building scalable, efficient, and interactive user interfaces in web applications.