React is an open-source JavaScript library for building user interfaces (UIs), primarily used for Single Page Applications (SPAs). It is maintained by Meta (formerly Facebook) along with a community of individual developers and companies.
Key Features and Concepts
Component-Based Architecture
React applications are built using self-contained, reusable UI components.
- Encourages modularity and maintainability
- Components can be composed to build complex UIs
Declarative Programming
Developers describe what the UI should look like for a given state, and React efficiently updates and renders it.
Virtual DOM
- React maintains a lightweight in-memory representation of the DOM.
- When state changes, React updates the Virtual DOM first, then calculates the minimal set of changes to apply to the real DOM.
- This approach significantly improves performance.
JSX (JavaScript XML)
- React uses JSX syntax, which lets you write HTML-like structures inside JavaScript.
- Makes UI definition more intuitive and integrated with application logic.
Unidirectional Data Flow
- Data flows one way: from parent to child components via
props. - Predictable data flow makes debugging and state management easier.
Hooks
- Introduced in React 16.8.
- Enable using state and lifecycle features inside function components without needing class components.
- Common hooks:
useState,useEffect,useContext, etc.
Purpose
React simplifies building interactive, dynamic, and data-driven UIs by providing:
- Efficient rendering with Virtual DOM
- Predictable data flow
- Reusable component model
- Scalable architecture
It is especially effective for applications where data changes frequently, making UI development more efficient, scalable, and less prone to bugs.