Setting Up Your First Node.js Application Step-by-Step
So far in this series, you’ve understood how Node.js works internally.
You know about its single-threaded nature, non-blocking behavior, and the event loop.
Now it’s time to actually use it.
This is where things start becoming real.
Installing Node.js
To begin, you need Node.js installed on your system.
Go to the official website of Node.js and download the recommended version for your operating system.
The installation process is straightforward and works similarly across Windows, macOS, and Linux.
Once installed, Node.js gives you:
a runtime to execute JavaScript
a command-line tool (
node)
Checking Installation
After installation, open your terminal or command prompt and run:
node -v
If everything is installed correctly, you will see a version number.
v18.x.x
You can also check npm (Node Package Manager):
npm -v
This confirms your environment is ready.
Understanding Node REPL
Before writing files, let’s understand something called REPL.
REPL stands for:
Read
Evaluate
Print
Loop
It is an interactive environment where you can write JavaScript and see the result instantly.
Start it by typing:
node
Now you can run code directly:
> console.log("Hello from REPL")
Hello from REPL
This is useful for quick testing and experimentation.
To exit:
.exit
Creating Your First JavaScript File
Now let’s move to actual coding.
Create a file called:
app.js
Inside it, write:
console.log("Hello from Node.js");
Running Your First Script
To run this file, go to the terminal and execute:
node app.js
Output:
Hello from Node.js
This is your first Node.js program running outside the browser.
Understanding What Just Happened
You wrote JavaScript in a file.
Node.js took that file, executed it using its runtime, and printed the result to the terminal.
You can visualize it like this:
app.js → Node.js runtime → Output in terminal
Writing Your First Server
Now let’s take a small step toward backend development.
Create a simple server.
const http = require("http");
const server = http.createServer((req, res) => {
res.end("Hello World from Node.js Server");
});
server.listen(3000, () => {
console.log("Server running on port 3000");
});
Running the Server
Run the file again:
node app.js
You will see:
Server running on port 3000
Now open your browser and go to:
http://localhost:3000
You will see:
Hello World from Node.js Server
Understanding the Flow
Here’s what is happening behind the scenes:
Browser → Request → Node.js Server → Response → Browser
Your server is now handling requests.
This is your first backend application.
Why This Matters
This step might feel simple, but it is important.
You have:
installed a runtime
executed JavaScript outside the browser
created your first server
handled a real HTTP request
This is the foundation of everything that comes next.
Final Thought
Node.js is not just about writing code.
It is about running JavaScript in a completely different environment.
Once you understand how to set it up and execute code, you are ready to build real applications.
