← Back to Chapters

React Overview & Features

⚛️ React Overview & Features

? Quick Overview

React is a JavaScript library used to create fast, interactive user interfaces. It focuses on building applications using components, which are reusable blocks that represent parts of the screen.

? Key Concepts

  • Components: Independent and reusable UI parts.
  • JSX: HTML-like syntax written inside JavaScript.
  • Virtual DOM: Improves performance by updating only changed elements.
  • One-way Data Flow: Makes debugging easier and predictable.

? Syntax & Theory

  • React builds UI using Components instead of full pages.
  • Components can be defined using functions or classes.
  • UI updates happen automatically when state changes.
  • ReactDOM handles placing content inside the actual browser DOM.

? Code Example – Hello React

? View Code Example 
// React example that displays a heading in the browser
<div id="root"></div>

<script type="text/babel">
const element = <h1>Hello, React!</h1>;
const root = ReactDOM.createRoot(document.getElementById("root"));
root.render(element);
</script>

? Live Output / Explanation

  • React selects the root div using the DOM.
  • The JSX element <h1> is converted to JavaScript.
  • render() displays content in the browser.
  • Virtual DOM ensures efficient updates if data changes.

? Tips & Best Practices

  • Always name components using PascalCase.
  • Each component must return one parent element.
  • Split UI into small reusable components.
  • Use console.log() to debug values.

? Try It Yourself

  1. Create an index.html file.
  2. Load React and ReactDOM using CDN links.
  3. Display the text Welcome to React Overview!.
  4. Add styling using inline JSX.
  5. Replace the text with your name using a variable.

Goal: Understand how React updates the screen using Virtual DOM.