Setting Up Your First Node.js Application Step-by-Step
If you want to build backend applications using JavaScript, the first thing you need is Node.js. It allows JavaScript to run outside the browser, making it possible to create servers, APIs, command-line tools, and much more.
In this beginner-friendly guide, you’ll learn how to:
Install Node.js
Verify the installation
Understand the Node REPL
Create and run your first JavaScript file
Build a simple Hello World server
By the end, you’ll have your very first Node.js application running successfully.
What is Node.js?
Node.js is a JavaScript runtime built on Chrome’s V8 JavaScript engine. In simple words, it allows you to run JavaScript directly on your computer instead of only inside a browser.
Before Node.js existed:
- JavaScript mostly worked only inside browsers
After Node.js:
- JavaScript could power servers and backend applications too
This made JavaScript a full-stack programming language.
Step 1: Installing Node.js
To start using Node.js, you first need to install it on your system.
Download Node.js
Visit the official website:
You’ll usually see two versions:
LTS (Recommended) → Stable and best for beginners
Current → Latest features
Choose the LTS version.
Installation Process
The setup is mostly the same across operating systems:
Download the installer
Open the installer
Click “Next” through the setup steps
Finish installation
Node.js automatically installs:
Node runtime
npm (Node Package Manager)
npm is used later to install libraries and tools.
Step 2: Checking the Installation
After installation, open your terminal or command prompt.
Run this command:
node -v
You should see an output similar to:
v22.1.0
This means Node.js is installed successfully.
Now check npm:
npm -v
Example output:
10.7.0
If both commands work, your setup is complete.
Understanding the Node REPL
Before writing actual files, it’s useful to understand something called the REPL.
What is REPL?
REPL stands for:
Read
Evaluate
Print
Loop
It is an interactive environment where Node.js reads your code, runs it instantly, shows the result, and waits for the next command.
Think of it like a calculator for JavaScript.
Starting the REPL
In your terminal, type:
node
You’ll see something like:
>
Now you can write JavaScript directly.
Example:
2 + 3
Output:
5
Another example:
const name = "Hitesh"
Then:
name
Output:
'Hitesh'
Exiting the REPL
To exit:
.exit
Or press:
Ctrl + C
twice.
Step 3: Creating Your First JavaScript File
Now let’s create an actual Node.js program.
Create a Project Folder
Create a new folder anywhere on your computer.
Example:
my-first-node-app
Open this folder in your code editor.
Create a JavaScript File
Inside the folder, create a file named:
app.js
Add this code:
console.log("Hello from Node.js");
Step 4: Running the Script Using Node
Open terminal inside your project folder.
Run:
node app.js
Output:
Hello from Node.js
Congratulations 🎉
You just executed your first Node.js application.
How Node Executes Your Script
Here’s the basic flow:
app.js → Node.js Runtime → Output in Terminal
Explanation
You write code in
app.jsNode.js reads the file
The V8 engine executes the JavaScript
Output appears in the terminal
Node Execution Flow Diagram
┌─────────────┐
│ JavaScript │
│ File │
│ (app.js) │
└──────┬──────┘
│
▼
┌─────────────┐
│ Node.js │
│ Runtime │
└──────┬──────┘
│
▼
┌─────────────┐
│ Console │
│ Output │
└─────────────┘
Step 5: Writing Your First Hello World Server
Now let’s create a very basic web server using Node.js.
Update your app.js file:
const http = require("http");
const server = http.createServer((request, response) => {
response.write("Hello World");
response.end();
});
server.listen(3000, () => {
console.log("Server is running on port 3000");
});
Understanding the Code
Importing the HTTP Module
const http = require("http");
Node.js provides built-in modules. The http module helps create web servers.
Creating the Server
http.createServer()
This creates a server that listens for requests from browsers.
Sending a Response
response.write("Hello World");
This sends text back to the browser.
Starting the Server
server.listen(3000)
This starts the server on port 3000.
Running the Server
Run the file again:
node app.js
You’ll see:
Server is running on port 3000
Now open your browser and visit:
http://localhost:3000
You should see:
Hello World
Your first Node.js server is now running successfully 🚀
Server Request Flow Diagram
Browser Request
│
▼
Node.js Server
│
▼
Response Sent Back
│
▼
Browser Displays Output
Common Beginner Mistakes
1. Wrong Folder in Terminal
If Node cannot find your file:
Error: Cannot find module
Make sure terminal is opened in the correct folder.
2. Typing File Name Incorrectly
This will fail:
node App.js
if your actual file name is:
app.js
File names are case-sensitive on many systems.
3. Port Already in Use
If port 3000 is busy, change:
server.listen(3000)
to another port like:
server.listen(5000)
Why Learning Node.js Matters
Node.js is widely used for:
Backend APIs
Real-time chat applications
Streaming platforms
Command-line tools
Full-stack JavaScript applications
Popular companies using Node.js include:
Netflix
PayPal
LinkedIn
Final Thoughts
You’ve now learned the complete basics of setting up your first Node.js application:
✅ Installed Node.js ✅ Verified installation ✅ Used the Node REPL ✅ Created your first JavaScript file ✅ Executed a script using Node ✅ Built a Hello World server
This is the foundation of backend development with JavaScript.
Your next step could be learning:
File handling
Modules
npm packages
Express.js
APIs and databases
But before moving ahead, make sure you are comfortable running Node scripts and understanding how the server works internally.