Setting Up Your First Node.js Application

🌱 Introduction — Let’s Set the Mood

Socho tum ek simple JavaScript developer ho jo ab tak sirf browser mein code chalata aaya hai — buttons, forms, animations… bas frontend ka duniya.

Ab ek din tum sochte ho:

👉 “Kya main backend bhi bana sakta hoon?”
👉 “Kya main apna server khud run kar sakta hoon?”

Aur yahin se start hota hai Node.js ka real magic.

Node.js tumhe allow karta hai JavaScript ko browser se bahar le jaane ke liye — matlab ab tum apna server, API, backend logic sab khud bana sakte ho.

Chapter 1: Introduction to Node.js

What is Node.js?

Node.js ek runtime environment hai jo JavaScript ko browser ke bahar run karne deta hai.

Simple meaning:

• Pehle JS sirf browser mein chalti thi

• Ab Node.js ki wajah se server par bhi chalti hai

Why Node.js?

• Fast execution (V8 engine use karta hai)

• Backend development ke liye perfect

• APIs, servers, real-time apps banane ke liye use hota hai

Chapter 2: Installing Node.js (OS Neutral Setup)

Step 1: Download

Official website:

Node.js Official Website

Always download LTS version

Step 2: Install

Installation steps (Windows / Mac / Linux same flow):

• Installer download karo

• Run karo

• Next → Next → Install

• Finish

Bas Node system mein install ho jata hai

Chapter 3: Verify Installation

Check Node

node -v

Explanation:

• node → runtime command

• -v → version check

Output:

v20.x.x

Check npm

npm -v

Explanation:

• npm = Node Package Manager

• packages install karne ke liye use hota hai

Chapter 4: Understanding Terminal + Project Setup

Step 1: Folder Create

mkdir my-first-node-app
cd my-first-node-app

Explanation:

• mkdir → folder banata hai

• cd → folder ke andar jata hai

Step 2: Initialize Project

npm init -y

Explanation:

• Node project initialize hota hai

• package.json file create hoti hai

• -y = default settings accept

package.json kya hai?

Ye project ka brain hota hai

Contains:

• Project name

• Version

• Dependencies

• Entry file

Chapter 5: First JavaScript File

Step 1: File create

app.js

Step 2: Code likho

console.log("Hello Node.js 👋");

Code Explanation:

console.log()

• Output print karta hai terminal mein

• Debugging ke liye use hota hai

String

• "Hello Node.js" simple message hai

Step 3: Run file

node app.js

Explanation:

• node → runtime start hota hai

• app.js → file execute hoti hai

Hello Node.js 👋

Chapter 6: Node REPL (Interactive Mode)

Node.js REPL ek interactive console hai jahan JS instant run hoti hai.

Start REPL

node

Prompt aata hai:

>

First Execution

5 + 10

Output:

15

Explanation:

• REPL code ko instantly evaluate karta hai

• File banane ki zarurat nahi hoti

Exit REPL

.exit

Chapter 7: How Node Executes Code

Simple Meaning:

Node ek engine ki tarah JS file ko run karta hai

Chapter 8: First HTTP Server (Real Backend Start)

const http = require("http");

const server = http.createServer((req, res) => {
  res.write("Hello World 👋");
  res.end();
});

server.listen(3000, () => {
  console.log("Server running on port 3000");
});

Line-by-Line Explanation:

1. Import module

const http = require("http");

• Built-in module load hota hai

• HTTP server banane ke liye use hota hai

2. Create server

const server = http.createServer((req, res) => {

• Server create hota hai

• req = request (browser se aaya data)

• res = response (hum bhejte hain)

3.Response

res.write("Hello World 👋");

Browser ko message bhejta hai

4.End Response

res.end();

Response complete karta hai

5.Start server

server.listen(3000);

Port 3000 par server run hota hai

6.Run Server

node app.js

Output:

Server running on port 3000

Browser:

Hello World 👋

Chapter 9: Server Working Flow