React JS - Library for Building User Interfaces

React is a free and open-source front-end JavaScript library, which is used to develop both web and mobile apps. It is used for handling the view layer for web and mobile apps. It gives you the ability to create reusable UI components. 

Features

• Component-Based Architecture: Reusable and modular components simplify development.
• Virtual DOM: Faster updates and rendering for improved performance.
• Declarative UI: Code is more predictable and easier to debug.
• Hooks: Simplifies state and lifecycle management in functional components.
• React Router: Enables efficient navigation and routing.
• Extensive Ecosystem: Compatible with tools like Redux, Next.js, and React Native.

Pros

• Performance: Virtual DOM ensures high efficiency.
• Flexibility: Suitable for both small and large-scale apps.
• Community Support: Large developer community and ecosystem.
• Cross-Platform Development: React Native extends React for mobile apps.
• SEO-Friendly: Can render on the server with tools like Next.js.

Cons

• Steep Learning Curve: Requires understanding JSX, hooks, and state management.
• Poor Documentation for Updates: Some features lack comprehensive documentation.
• Rapid Changes: Frequent updates can cause compatibility challenges.
• Heavy Dependency on Third-Party Tools: Native functionality is limited.

Pricing

React.js is completely free and open-source, licensed under MIT. Developers can use it without restrictions for commercial or non-commercial projects.