React JS (or simply React) is an open-source JavaScript library used for building user interfaces (UIs), especially single-page applications (SPAs) where the content updates dynamically without reloading the entire page.

Key Features of React JS:

Component-Based Architecture

UI is built using components, which are reusable pieces of code (like buttons, forms, etc.).

Each component manages its own logic and rendering.

Declarative Syntax

You describe what the UI should look like, and React takes care of updating it when data changes.

Virtual DOM (Document Object Model)

React uses a lightweight copy of the actual DOM to optimize performance.

It updates only the parts of the DOM that change, instead of reloading the entire page.

JSX (JavaScript XML)

JSX allows you to write HTML-like syntax inside JavaScript, making it easier to visualize the UI structure.

Unidirectional Data Flow

Data flows in one direction, from parent to child components, making it easier to debug and manage.

React Hooks

Hooks (like useState, useEffect) let you manage state and side effects in functional components without writing classes.

Common Use Cases:

Building interactive web apps (e.g., Facebook, Instagram)

Creating dashboards or admin panels

Developing progressive web apps (PWAs)

Who Maintains React?

React was developed by Facebook (now Meta) and is actively maintained by Meta and the open-source community.