React.js is a popular JavaScript library developed by Facebook for building user interfaces (UIs), especially for single-page applications (SPAs). It's component-based, which means the UI is broken into reusable parts (components), making development faster, more modular, and easier to manage.

💡 Key Features of React:

• ⚛️ Component-Based: Build encapsulated components that manage their own state.

• ⚡ Virtual DOM: Efficient updates and rendering using a lightweight copy of the actual DOM.

• 🔄 One-Way Data Binding: Data flows in one direction for better control.

• 🧠 Declarative: Describe what you want the UI to look like, and React takes care of the DOM updates.