Introduction to React

What is React?

React is a JavaScript library for building user interfaces, created by Facebook (now Meta) in 2013. It lets you build complex UIs from small, reusable pieces called components.

React uses a Virtual DOM — a lightweight copy of the real DOM. When your data changes, React calculates the minimal set of changes needed and updates only those parts of the page, making it extremely fast.

React follows a component-based architecture. Instead of writing one large HTML file, you break your UI into independent, reusable components that manage their own state and compose together to form complex interfaces.

• Component-Based — Build encapsulated components that manage their own state
• Declarative — Describe what the UI should look like, React handles the updates
• Virtual DOM — Efficient rendering by minimizing real DOM manipulations
• One-Way Data Flow — Data flows from parent to child via props
• Huge Ecosystem — React Router, Redux, Next.js, and thousands of libraries

// A simple React component
function Welcome() {
  return <h1>Hello, Priodemy!</h1>;
}

// Using the component
function App() {
  return (
    <div>
      <Welcome />
      <p>Welcome to React!</p>
    </div>
  );
}

Why Learn React?

React is one of the most popular frontend technologies in the world. It powers Facebook, Instagram, Netflix, Airbnb, and thousands of other production applications.

Learning React opens doors to mobile development with React Native, server-side rendering with Next.js, and a massive job market for React developers.

• Most in-demand frontend skill in the job market
• Reusable components save development time
• Strong community and extensive documentation
• React Native lets you build mobile apps with the same skills
• Next.js enables server-side rendering and static sites