Node.js Fundamentals & npm

Node.js Fundamentals & npm

Node.js is a server‑side JavaScript runtime built on Chrome’s V8 engine. It lets you run JavaScript outside the browser and power APIs, CLI tools, servers, and more.

1️⃣ Install Node.js

• Windows / macOS / Linux: download the installer from https://nodejs.org or use a version manager such as nvm (nvm install --lts).
• Verify:

node -v   # e.g. v20.8.0
npm -v    # npm version

2️⃣ The REPL & core globals

$ node
> console.log('Hello from Node');
> process.argv   // command‑line arguments array
> __dirname      // directory of the current module
> __filename     // absolute path of the current file

3️⃣ Modules – CommonJS (require/module.exports)

// utils.js
function add(a,b){ return a+b; }
module.exports = { add };
// app.js
const {add} = require('./utils');
console.log(add(2,3));

4️⃣ npm – the package manager

# initialise a project (creates package.json)
npm init -y

# install a library as a runtime dependency
npm install axios

# install a dev‑only tool
npm install --save-dev jest

package.json scripts let you run commands easily:

"scripts": { "start": "node app.js", "test": "jest" }

Run with npm start or npm test.

5️⃣ Environment variables

Create a .env file and load it with dotenv:

npm install dotenv

require('dotenv').config();
console.log(process.env.API_KEY);

Node gives you full access to the file system, networking, and many built‑in modules (fs, http, path, etc.).