Getting Started with Node.js
Why Do We Need Node.js?
Imagine you already know JavaScript from the browser.
You can:
change webpage content
handle button clicks
create interactive UI
But what if you want JavaScript to:
create servers
read files
build APIs
work outside the browser
That’s where Node.js comes in.
Node.js allows JavaScript to run on your computer directly, not just inside a browser.
What is Node.js?
Node.js is a JavaScript runtime.
Simple meaning:
It lets your computer understand and run JavaScript files.
Without Node.js:
JavaScript → Browser only
With Node.js:
JavaScript → Browser + Computer
How Node.js Works
Installing Node.js
To install Node.js:
Go to the official website of Node.js
Download the LTS version
Install normally like other software
LTS means:
Long Term Support (stable version)
Checking if Node.js is Installed
Open your terminal and run:
node -v
If installed correctly, you’ll see something like:
v22.5.0
Check npm Too
npm comes with Node.js.
Run:
npm -v
You’ll see a version number.
npm helps install packages later.
What is the Node REPL?
Before writing files, Node.js gives us something called REPL.
REPL stands for:
Read
Evaluate
Print
Loop
Sounds complex, but it’s simple.
Think of it like a JavaScript playground inside your terminal.
Starting the REPL
Run:
node
You’ll see:
>
Now you can directly write JavaScript.
Example:
2 + 3
Output:
5
Why REPL is Useful
REPL is great for:
quick testing
practicing JavaScript
checking small logic
Example:
let name = "Aman";
console.log(name);
Instant output.
No file needed.
Exiting the REPL
To exit:
.exit
Or press:
Ctrl + C (twice)
Creating Your First JavaScript File
Create a file:
app.js
Inside it:
console.log("Hello Node.js");
Running the File
Open terminal in the same folder and run:
node app.js
Output:
Hello Node.js
Your First Node.js Server
Now let’s create a tiny web server.
Replace your code with this:
const http = require('http');
const server = http.createServer((req, res) => {
res.end('Hello World');
});
server.listen(3000, () => {
console.log('Server running on port 3000');
});
Running the Server
Run:
node app.js
Terminal output:
Server running on port 3000
Now open browser and visit:
http://localhost:3000
You’ll see:
Hello World
Breaking Down the Server Code
Importing HTTP Module
const http = require('http');
Node.js already provides an HTTP tool.
We import it.
Creating the Server
const server = http.createServer((req, res) => {
});
This creates a server.
req→ incoming requestres→ response we send back
Sending Response
res.end('Hello World');
This sends text to the browser.
Starting the Server
server.listen(3000);
This starts the server on port 3000.
Think of a port like a door your app listens on.
Before vs After Node.js
Without Node.js
JavaScript only inside browser
With Node.js
JavaScript can create servers, APIs, tools, scripts
Much more powerful.
Practice Assignment
1. Check Installation
Run:
node -v
npm -v
2. Use REPL
Start REPL:
node
Try:
addition
variables
console.log
3. Create First File
Create:
test.js
Write:
console.log("Learning Node.js");
Run it.
4. Modify the Server
Change:
Hello World
to your own custom message.
5. Change Port Number
Try:
4000
5000
Observe what changes in browser URL.
