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Tutorials/React & Next.js/Ch 1: Beginner: What is React? Components, JSX & useState Hook
Frameworks

React 19 & Next.js 15 — Beginner to Full-Stack Architecture

Track Progress33%
10 HoursLevel: All Levels
Chapter 1 of 3🟢 Beginner⏱️ 9 min read

Beginner: What is React? Components, JSX & useState Hook

Learn how React breaks UIs into reusable LEGO blocks (Components), write JSX, and make interactive click counters with useState.

👶 Beginner Primer (Explain Like I'm 5):

A React Component is like a custom LEGO brick: you build a <Button /> brick once, and you can snap it onto your navbar, card, or modal 50 times without re-inventing the brick.

Building User Interfaces with Reusable Components

In standard JavaScript, updating UI requires manually selecting DOM elements and changing text. In React, your UI is an automatic reflection of your State:

text
UI = f(state)

1. What is JSX?

JSX allows you to write HTML-like tags directly inside JavaScript!

jsx
function WelcomeCard({ name }) {
  return <h1>Hello, {name}!</h1>;
}

2. What is State (useState)?

State is memory inside a component. When state changes, React automatically re-renders the component to display the new value!

Intuitive Mental Model

Think of React state as a score counter on an arcade machine: whenever you score a point, the digital display updates automatically.

Engineering Pro-Tips
  • ✓Never mutate state directly (e.g. count = 5 is an error). Always call setCount(5).
Junior Pitfalls & Anti-Patterns
  • ✕Trying to use React hooks outside of a React component.