What is Node.js?

By the end of this lesson you will be able to:

1. Explain in one sentence what Node.js is and why it exists.
2. Check your Node version in a terminal with node --version.
3. Write a .js file and run it from the terminal with node hello.js.
4. Name two things Node can do that browser JavaScript cannot.

In Level 2 you ran JavaScript inside the browser — clicking buttons, changing the page, fetching data. The browser gave you helpers like document and window.

Look at this two-line script. Read it, then predict:

console.log('Hello from JavaScript!')
document.querySelector('h1')

Predict together

• Which line prints a message you can read?
• The word document means “the web page”. If there is no web page, what might go wrong on line 2?

Think of a fish that has only ever lived in one tank. It can swim, but only there. Node.js is like moving that fish into a whole river — same fish, far more places to go.

For years, JavaScript could only run inside a browser. Then people took the browser's JavaScript engine — the part called V8, the same one inside Chrome — and wrapped it so it could run anywhere on your computer. That wrapper is Node.js.

Node.js — a program that runs JavaScript files directly on your computer, without any browser. We call it a runtime: the thing that runs your code.

The smallest possible Node program

Make a file called hello.js with one line inside:

console.log('Hello from Node!')

Then, in a terminal, run it by typing:

$ node hello.js

You will see the message printed straight into the terminal:

Hello from Node!

Browser JavaScript vs Node JavaScript

Same language, different powers:

Why it matters

Every backend in Level 3 runs on Node. So does the tooling you already use — Vite, npm, even this course's build. Learn Node once, and you write JavaScript for both sides of a website: the browser and the server.

Follow along on your own machine. You will need a terminal — the built-in one in VS Code is perfect. Open it with Terminal → New Terminal from the top menu.

Step 1 — Check Node is installed

Type this and press Enter:

$ node --version

If Node is installed, you will see a version number:

v22.14.0

No version, or a “command not found” error? Go to nodejs.org, download the LTS version (LTS = “Long-Term Support”, the stable one), install it, then close and reopen the terminal and try again.

Step 2 — Make a file

In VS Code, make a new file called hello.js. Type this in — a friendly greeting for Aisyah:

const name = 'Aisyah'
console.log('Selamat datang, ' + name + '!')

Step 3 — Run it

Back in the terminal, run the file by name:

$ node hello.js

Selamat datang, Aisyah!

No browser. No HTML. Node read your file, ran it top to bottom, and printed the result. That is the whole idea.

Step 4 — Do something the browser can't

Node gives you a special object called process with facts about the computer it is running on. The browser has no such thing. Add these two lines to hello.js:

console.log('Node version:', process.version)
console.log('Running on:', process.platform)

Run it again with node hello.js. Now you also see:

Selamat datang, Aisyah!
Node version: v22.14.0
Running on: win32

What changed? Your script now reports facts about your machine — the Node version and the operating system (win32, darwin for Mac, or linux). Browser JavaScript can never reach that.

Three tasks, all run with node <filename> in the terminal. Keep each one in its own file.

1. Task 1 — Make it yours

   Open hello.js. Change the name and greeting to your own, and add a line about your favourite food, for example:

   console.log('My favourite food is nasi lemak.')

   Run it and check both lines appear in the terminal.

2. Task 2 — A little maths

   Make a new file total.js. Store the price of two snacks in variables (in RM), add them, and print the total. Start from this shape and fill in the blanks:

   const tehTarik = 2.5
   const kuih = 1.5
   const total = tehTarik + kuih
   console.log('Total: RM', total)

   Run node total.js. Did it print Total: RM 4?

3. Task 3 — Introduce yourself

   Make about.js. Using a template literal (backticks and ${ } from Level 2), print three lines about yourself — your name, your town, and one thing you want to build. Run it with Node.

Write a script called receipt.js that prints a tidy receipt for three items from a mamak stall. Use everything so far: variables, arithmetic, and running the file with Node.

It works if: running node receipt.js prints three item lines and a correct total in RM at the bottom.

// receipt.js — a mamak order for Wei Jie
const rotiCanai = 1.5
const milo = 3.0
const magaGoreng = 7.5
const total = rotiCanai + milo + magaGoreng

console.log('--- Mamak Receipt ---')
console.log('Roti canai:  RM', rotiCanai)
console.log('Milo ais:    RM', milo)
console.log('Maggi goreng: RM', magaGoreng)
console.log('---------------------')
console.log('Total:       RM', total)

--- Mamak Receipt ---
Roti canai:  RM 1.5
Milo ais:    RM 3
Maggi goreng: RM 7.5
---------------------
Total:       RM 12

• Node.js runs JavaScript on your computer, with no browser needed.
• It uses V8 — the very same engine that runs JavaScript inside Chrome.
• Run a file from the terminal with node <filename>.
• Node has no document or window — there is no web page.
• Node can reach files, the network, and machine facts (via process) — the browser can't.

New words

• Runtime — the program that runs your code (Node is a JavaScript runtime).
• Terminal (CLI) — the typing window where you run commands like node.
• V8 — the fast JavaScript engine shared by Chrome and Node.