⚛️ React Day 1 — From Java to JSX( JavaScript XML) My First Frontend App Setup!

⚛️ React Journey Day 1: From Zero to Hello World (With Java Dev Mindset)

Hey folks! 👋 Welcome to Day 1 of my Full Stack Journey — and today, we officially begin learning React, from scratch, as a backend developer!

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🚀 Why Do We Need Node.js and npm to Run React?

If you’re from a Java background like me, think of this:

Concept	Java	React
Language	Java	JavaScript (JSX)
Runtime	JRE / JDK	Node.js
Build Tool	Maven / Gradle	npm (Node Package Manager)

Node.js allows JavaScript to run outside the browser. React apps use Node to:

• Compile JSX into plain JS
• Run local development servers
• Install libraries (just like Maven dependencies)

npm is like Maven — it downloads, installs, and manages your frontend packages and scripts.

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🔧 What is Vite? And Why Do We Use It?

Vite is a modern build tool that gives us:

• Instant startup
• Faster hot reload
• Simple setup

It's like the Spring Boot Initializr of the frontend world! 🧠

Feature	Spring Boot	Vite
Project Setup	start.spring.io	npm create vite
Dev Server	Embedded Tomcat	Vite Dev Server

🔄 Alternatives to Vite

• create-react-app (CRA) – older, heavier setup
• Parcel – zero config but less popular
• Webpack (manual) – expert level
• Next.js – production-ready framework on top of React

🔥 Today, Vite or Next.js is preferred in companies

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📦 Setting Up React Project — Step-by-Step

✅ Prerequisite: Install Node.js (Mac & Windows)

Go to https://nodejs.org and download the LTS version:

• 🍏 Mac users: Download the macOS installer (.pkg)
• 🪟 Windows users: Download the Windows installer (.msi)

After installation, open Terminal or Command Prompt and run:

node -v
npm -v

🍏 Optional for Mac Users: If you use or want to use Homebrew (Mac’s terminal-based package manager), install Node with:

/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
brew install node

Otherwise, download the Node.js macOS installer (.pkg) from nodejs.org.

🧠 React Setup Commands — Explained Step-by-Step (for Java Devs)

npm create vite@latest my-react-app -- --template react
cd my-react-app
npm install
npm run dev

✅ 1. npm create vite@latest my-react-app -- --template react

This command scaffolds a new React project using the latest version of Vite.

Part	Meaning
npm	Node’s package manager — like mvn or gradle
create vite@latest	Use the latest official Vite project generator
my-react-app	Your app/project folder name
--	Separates npm arguments from Vite ones
--template react	Use React as the frontend template

Java Analogy: Like using Spring Initializr with a web dependency and generating a project zip.

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✅ 2. cd my-react-app

Change directory into the newly created React app folder.

Java Analogy: cd my-spring-app after generating a project using start.spring.io.

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✅ 3. npm install

Installs all dependencies defined in package.json — React, Vite, JSX tooling, etc.

Java Analogy: Like mvn install to download all dependencies from pom.xml.

📦 What Does npm install Do?

This command installs all the dependencies listed in your project’s package.json.

• 📥 Downloads required libraries (React, Babel, Vite, etc.)
• 🧱 Creates a node_modules/ folder — like your local dependency JARs
• 🧾 Generates a package-lock.json to lock versions

Think of it like running:

mvn install

in a Spring Boot project. It resolves and pulls all required dependencies.

🧠 Java Comparison

React (npm)	Java (Maven)
npm install	mvn install
Reads package.json	Reads pom.xml
Creates node_modules/	Uses .m2/repository
Creates package-lock.json	No exact lock, but fixed versions in <version>

🔒 What is package-lock.json and Why Is It Important?

When you run npm install, it not only installs your dependencies but also creates a special file called package-lock.json.

🧠 What It Does

• Locks the exact versions of all dependencies (and their sub-dependencies)
• Ensures everyone on your team uses the same versions
• Makes builds predictable and stable

"axios": {
  "version": "1.4.0",
  "resolved": "https://registry.npmjs.org/axios/-/axios-1.4.0.tgz"
}

🚫 What Happens Without It?

• You install axios@1.4.0
• Your teammate installs axios@1.4.5
• Unexpected bugs may crash production 💥

🧠 Java Analogy

React (npm)	Java (Maven)
package.json with ^1.4.0	<version>[1.4.0,2.0.0)</version>
package-lock.json	Pinning versions or lock plugin (in Gradle)

✅ Summary

• package-lock.json = your project's version snapshot
• Protects you from bugs in new versions
• Ensures consistent builds across all machines

✅ When Should You Run It?

• 📁 After downloading or cloning a React project
• 🔄 After deleting node_modules/
• ➕ After adding new dependencies like npm install axios

⚠️ Important Notes

• 🚫 Never push node_modules/ to GitHub
• ✅ Only commit package.json and package-lock.json

Once installed, you’re ready to run:

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✅ 4. npm run dev

Starts the Vite development server.

• Hot reload enabled 🔁
• Watches for code changes 👀
• Serves your app on http://localhost:5173 🌐

Java Analogy: Like ./mvnw spring-boot:run to launch your backend locally.

⚙️ What Does npm run dev Actually Do?

This command tells npm (Node Package Manager) to run the script named dev from your project’s package.json file.

"scripts": {
  "dev": "vite",
  "build": "vite build",
  "preview": "vite preview"
}

So when you run npm run dev, it executes Vite — your development server.

🔍 What Happens Internally?

• 🟢 Starts Dev Server → Runs at http://localhost:5173
• 🔁 Hot Reload → Instantly reloads browser on code changes
• ⚡ Compiles JSX → Converts JSX to regular JavaScript using ESBuild
• 📁 Serves Static Files → Loads from public/ and src/

✅ It's optimized for speed and instant feedback — perfect for development!

🧠 Java Comparison

React (Vite)	Java (Spring Boot)
npm run dev	mvn spring-boot:run
Starts Vite dev server on port 5173	Starts embedded Tomcat on port 8080
Hot-reloads UI as you type	Rebuild + restart on code changes

💡 Why Use npm run dev Instead of Just vite?

• ✅ Ensures the right version of Vite is used from your local project
• ✅ Reads any custom configs from vite.config.js
• ✅ More portable — works for all devs on your team

🎯 Summary

• npm run dev starts the Vite server using your project’s local config
• It’s fast, hot-reload enabled, and watches your JSX/TSX code
• It's the frontend version of spring-boot:run for Java devs

🌐 You can now open http://localhost:5173 in your browser and start building your UI!

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📦 What’s Inside package.json?

You’ll see these scripts under the scripts section:

{
  "scripts": {
    "dev": "vite",
    "build": "vite build",
    "preview": "vite preview"
  }
}

So when you run npm run dev, it’s just calling vite under the hood.

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🧠 Summary Table

Command	What It Does	Java Equivalent
npm create vite@latest my-app -- --template react	Create a new React app using Vite	start.spring.io project creation
cd my-app	Enter the project folder	cd my-springboot-app
npm install	Install frontend dependencies	mvn install
npm run dev	Run Vite dev server with hot reload	mvn spring-boot:run

🎉 After this, you can open http://localhost:5173 in your browser and see your first React component in action!

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📁 Folder Structure — Compared with Java

Java Project	React Project
src/main/java	src/ (JSX code)
src/main/resources	public/ (static files)
pom.xml	package.json

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🧠 Your First Component (App.jsx)

Open App.jsx and write:

function App() {
  return (
    <div>
      <h1>Hello Anand!</h1>
      <p>This is your first React component.</p>
    </div>
  );
}

export default App;

Java Comparison:

• function App() = like a public class
• return (<div>) = like HTML template builder
• export default App = like your main class being exposed

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🧩 What is JSX?

JSX = JavaScript + XML

It allows us to write:

<h1>Hello</h1>

inside JavaScript functions. It’s not natively supported by browsers, so tools like Babel (inside Vite) convert it to valid JS.

Supported File Extensions:

• .js — Plain JavaScript
• .jsx — JavaScript with JSX
• .ts — TypeScript
• .tsx — TypeScript with JSX

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🎯 Mini Practice

function App() {
  const name = "Anand";
  const year = new Date().getFullYear();

  return (
    <div>
      <h2>🚀 Hello {name}!</h2>
      <p>React Journey — {year}</p>
      <button onClick={() => alert("Keep Learning!")}>Motivate Me</button>
    </div>
  );
}

Try it, run it, and smile when the alert works 😄

FILE : /my-react-app/src/App.jsx

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✅ Wrapping Up

• You now know what Node.js & npm are — like JDK + Maven
• Vite is your Spring Boot of the frontend
• JSX is HTML + JavaScript (JSX = JavaScript + XML)
• You created and ran your first React component!

✅ From Day 2 onward: I’ll start using .tsx files — because most companies today expect React with TypeScript.
It's strongly typed, safer, and aligns well with enterprise-grade standards. 💼⚛️🟦

Stick around — React is just getting fun! ⚛️

If you liked this post or are following the same path, drop a comment below — let’s learn React + TypeScript together! 💬🔥