Node.js Runtime Basics

What you will practice

• Check that Node.js and npm are installed.
• Create and run a real `.js` file from the terminal.
• Use Node-only globals such as `process.cwd()` and `process.argv`.

What this means

JavaScript is the language. Node.js is a runtime: a program that runs JavaScript outside the browser.

In the browser you usually work with pages, buttons, forms, `document`, and `window`. In Node.js you usually work with files, terminal arguments, packages, environment variables, network sockets, and server processes.

A beginner should start with the real workflow: create a file, run `node file.js`, read the terminal output, change the file, and run it again.

Mini glossary

Runtime

The environment that executes code and provides built-in abilities.

Server-side

Code that runs on a server or local machine, not inside the user's page.

DOM

Browser page APIs that Node.js does not provide by default.

How it works step by step

1. Run `node -v` to check the Node.js runtime version.
2. Run `npm -v` to check that the package manager is available.
3. Create `hello-node.js` and run it with `node hello-node.js`.
4. Change the script and run the command again. This edit-run-read loop is the foundation of Node.js learning.

Where you will use this

• A Node.js script converts files or generates reports.
• A backend API receives requests from a website or mobile app.
• A build tool compiles, bundles, tests, or checks frontend code.

Before you run the code

These examples are intentionally pure Node.js. They do not use Express, Next.js, TypeScript, Babel, or any framework.

Run them in your terminal. The browser runner is disabled here because real Node.js APIs should run in Node.js, not in a web page.

Run it locally

These examples are meant for a local Node.js project. Create the files shown below, then run the terminal commands from the project folder.

node -v
npm -v

mkdir lumio-node-start
cd lumio-node-start
touch hello-node.js

const name = process.argv[2] || "student";

console.log(`Hello from Node.js, ${name}!`);
console.log(`Current folder: ${process.cwd()}`);
console.log(`Node version: ${process.version}`);

node hello-node.js
node hello-node.js Mira

Common beginner mistakes

• Expecting `document` or `window` to exist in Node.js.
• Thinking Node.js is a different language from JavaScript.
• Running untrusted code on a server without isolation.

Try changing this next

• Run `node hello-node.js Sasha` with a different name.
• Add `console.log(process.argv)` and inspect the terminal output.
• Run the file from a different folder and compare `process.cwd()`.