REACT

#javascript #react #ai

About react:

React is a JavaScript library for building user interfaces.
React is used to build single-page applications.
React allows us to create reusable UI components.

React (also known as React.js or ReactJS) is a free and open-source front-end JavaScript library that aims to make building user interfaces based on components more "seamless". It is maintained by Meta (formerly Facebook) and a community of individual developers and companies. According to the 2025 Stack Overflow Developer Survey, React is one of the most commonly used web technologies.

React can be used to develop single-page, mobile, or server-rendered applications with frameworks like Next.js and React Router. Because React is only concerned with the user interface and rendering components to the DOM, React applications often rely on libraries for routing and other client-side functionality. A key advantage of React is that it only re-renders those parts of the page that have changed, avoiding unnecessary re-rendering of unchanged DOM elements. React is used by an estimated 6% of all websites.

React is a JavaScript library used to build interactive UI (User Interfaces), mainly for web apps.

It was developed by Facebook (Meta) and is widely used in companies like Instagram, Netflix, etc.

Why React is used?

Fast
Reusable
Easy to manage

3 Core Concepts That Make React Work

1. Components (The Lego Bricks)

React splits the UI into independent, reusable pieces called Components. For example, on a page like UI, a navigation bar, a sidebar, and a video player are all separate components.

You write a component once (like a Button) and reuse it across your entire app.

Components are typically written using JSX (JavaScript XML), a syntax extension that lets you write HTML-like code directly inside your JavaScript.

2. State and Props (The Data Flow)

Data in React moves in two ways:

Props (Properties): Think of these as configuration settings passed down from a parent component to a child component (like telling a button component what text to display). Props are read-only.

State: This is a component's private, internal memory. If a user clicks a "Like" button, the count increases. That count is stored in the component's state. When state changes, the component automatically updates.

3. The Virtual DOM (The Speed Demon)

Traditionally, when data changes on a website, the browser has to recalculate and redraw the entire webpage. This is slow and performance-heavy.

React solves this by creating a Virtual DOM—a lightweight, digital copy of the actual webpage kept in the computer's memory.

When state changes, React updates the Virtual DOM first.
It then compares the new Virtual DOM with a snapshot of the old one (a process called "diffing algorithm").
React figures out exactly which tiny part changed and updates only that specific piece on the real screen, leaving the rest untouched.

Why Developers Choose React

Declarative UI: You simply describe what the UI should look like based on the current data state, and React handles all the complex steps to update the screen.

Massive Ecosystem: Because of its popularity, React has thousands of pre-built packages for routing, styling, and state management, plus React Native for building mobile apps.

High Performance: The Virtual DOM ensures applications stay snappy even when handling complex, real-time data streams.