React.js is a popular open-source JavaScript library used for building user interfaces, particularly for single-page applications. Developed and maintained by Facebook, React allows developers to create reusable UI components and efficiently manage application state with a virtual DOM.

Features of React.js:

• Component-based architecture that promotes reusability and maintainability.
• Virtual DOM for efficient rendering and improved application performance.
• Unidirectional data flow to ensure predictable state management.

To get started with React.js, run the following commands: $ cd my-app
$ npm start

Disclaimer: React.js is open-source software distributed under the MIT License. It is not affiliated with, endorsed by, or sponsored by any other company. React.js is provided "as is," without any warranty, express or implied. Users utilize this software at their own risk. The developers and contributors to React.js hold no responsibility for any damages, losses, or consequences resulting from the use of this software. Users are advised to carefully review and comply with licensing terms and any applicable regulations while using React.js.