If you want to become a backend developer, Node.js is one of the best technologies to learn.

With Node.js, you can:

• Build servers

• Create APIs

• Work with databases

• Build real-time applications

• Use JavaScript outside the browser

In this article, we’ll set up our very first Node.js application step-by-step.

We’ll cover:

• Installing Node.js

• Checking installation using terminal

• Understanding Node REPL

• Creating your first JavaScript file

• Running scripts using the node command

• Writing a simple Hello World server

Let’s begin.

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What Is Node.js?

Node.js is a JavaScript runtime that allows JavaScript to run outside the browser.

Normally, JavaScript runs inside browsers like:

• Chrome

• Firefox

• Edge

But Node.js allows JavaScript to run directly on your computer or server.

This makes backend development possible using JavaScript.

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Step 1: Installing Node.js

To use Node.js, first install it on your system.

Download Node.js from the official website:

Node.js Official Website

Install the:

LTS (Long Term Support) version

because it is stable and recommended for beginners.

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What Gets Installed?

When you install Node.js, two important things are installed:

Tool	Purpose
Node.js	Runs JavaScript outside browser
npm	Package manager for installing libraries

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Step 2: Check Installation

After installation, open your terminal or command prompt.

Run:

node -v

Example output:

v22.0.0

This confirms Node.js is installed successfully.

Now check npm:

npm -v

Example output:

10.5.0

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Understanding the Terminal

The terminal is where we run Node.js commands.

Examples:

node app.js
npm install

Backend developers use the terminal very frequently.

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Step 3: Understanding Node REPL

REPL stands for:

Read
Evaluate
Print
Loop

It is an interactive environment where Node.js executes JavaScript instantly.

Start REPL by typing:

node

You’ll see something like:

>

Now you can run JavaScript directly.

Example:

2 + 3

Output:

5

---

Why REPL Is Useful

REPL is great for:

✅ Testing small code snippets ✅ Practicing JavaScript ✅ Debugging quickly ✅ Experimenting with logic

---

REPL Flow

Write Code
     ↓
Node Executes
     ↓
Result Printed
     ↓
Wait for Next Input

---

Step 4: Create Your First JavaScript File

Create a folder for your project.

Example:

my-first-node-app

Inside it, create a file:

app.js

---

Write Your First Node.js Code

Inside app.js:

console.log("Hello Node.js");

This is your first Node.js program.

---

Step 5: Run the Script Using Node

Open terminal inside the project folder.

Run:

node app.js

Output:

Hello Node.js

Congratulations 🎉

You just executed your first Node.js application.

---

Node Execution Flow

app.js
   ↓
Node Runtime
   ↓
JavaScript Executes
   ↓
Output Printed in Terminal

---

Understanding What Happened

When you run:

node app.js

Node.js:

1. Reads the file

2. Executes JavaScript code

3. Prints output to terminal

Simple but powerful.

---

Step 6: Writing Your First Hello World Server

Now let’s create a basic web server.

Replace the code inside app.js with:

const http = require("http");

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

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

---

Understanding the Code

Import HTTP Module

const http = require("http");

Node.js has a built-in HTTP module for creating servers.

---

Create Server

http.createServer()

creates a server.

---

Handle Request and Response

(req, res)

• req → incoming request

• res → server response

---

Send Response

res.end("Hello World");

sends data back to the browser.

---

Start Server

server.listen(3000)

starts the server on port 3000.

---

Run the Server

In terminal:

node app.js

Output:

Server running on port 3000

Now open browser:

http://localhost:3000

You’ll see:

Hello World

Your first Node.js server is now running.

---

Server Request Flow

Browser Request
      ↓
Node Server Receives Request
      ↓
Server Sends Response
      ↓
Browser Displays Result

---

Why This Is Important

This small server is the foundation of backend development.

Every backend application works similarly:

• Client sends request

• Server processes request

• Server sends response

---

Common Beginner Mistakes

Forgetting to Save File

Always save changes before running.

---

Wrong File Name

Make sure:

node app.js

matches your actual filename.

---

Port Already in Use

If port 3000 is busy, try another port:

server.listen(5000)

---

Practice Assignment

Try these exercises yourself.

---

1. Install Node.js

Verify installation using:

node -v
npm -v

---

2. Use REPL

Run:

node

Try:

10 + 20
"Hello".toUpperCase()

---

3. Create Your Own JS File

Create:

test.js

Print:

console.log("Learning Node.js");

Run it using:

node test.js

---

4. Modify the Server Response

Change:

res.end("Hello World");

to something custom.

Example:

res.end("Welcome to Node.js");

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Final Thoughts

Setting up your first Node.js application is the beginning of backend development.

In this article, you learned:

• How to install Node.js

• How to verify installation

• What REPL is

• How to run JavaScript files

• How to create a simple server

The key idea is:

Node.js allows JavaScript to run outside the browser.

This opens the door to building:

• APIs

• Backend servers

• Real-time applications

• Full-stack projects

Once you are comfortable with basic Node.js setup, you can move toward:

• Express.js

• Databases

• Authentication

• REST APIs

and real-world backend systems.

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And now, you know how to set up your first Node.js application step-by-step.

If you have any doubt or want to connect, feel free to drop a comment — I’d be happy to help.

Thanks for reading, and see you in the next blog!

Peace ✌️ and Happy Learning!