Node.js Overview

Introduction

Node.js runs JavaScript on servers, CLIs, and build tools—not in a browser tab. The language syntax matches what you learned earlier; the APIs change (files, processes, HTTP servers instead of DOM). This chapter explains what Node is, how it differs from browser JS, and where it fits in full-stack work.

Prerequisites

What is JavaScript
Node.js LTS installed (Windows, macOS, or Linux)

What Is Node.js

Node.js is a runtime built on Chrome’s V8 engine. It executes .js files on your machine and provides system-level APIs:

Read/write files (fs)
Create HTTP servers (http, https)
Spawn child processes
Access environment variables (process.env)

npm (Node Package Manager) ships with Node for installing libraries.

Browser vs Node

Topic	Browser	Node.js
UI	DOM, CSS, events	No DOM (use HTML files + browser for UI)
Global object	`window`	`globalThis` / `global`
Modules	ES modules in `<script type="module">`	ES modules or CommonJS files
Storage	`localStorage`	Files, databases, Redis, etc.
Network	`fetch` (CORS rules)	`fetch`, `http`, TCP clients

Core language features—functions, classes, Promises, arrays—work in both.

Run Your First Server Script (Preview)

javascript

// hello-server.mjs — run: node hello-server.mjs
console.log("Node version:", process.version);
console.log("Platform:", process.platform);

bash

node hello-server.mjs

Full HTTP example in Node HTTP server.

Typical Node Use Cases

REST and GraphQL APIs
SSR and static site tooling (Next.js, Vite)
CLIs and automation scripts
WebSocket and streaming services
Background jobs and queues

Same Language, Different Ecosystem

Front-end bundles often target browsers; Node projects target server runtimes. You may share validation logic in a monorepo, but do not import document in server code or fs in browser code without bundler shims.

Mini Example: CLI Greeting

javascript

// greet.mjs
const name = process.argv[2] ?? "Guest";
console.log(`Hello, ${name} from Node`);

bash

node greet.mjs Ada

FAQ

Is Node “backend only”?

Mostly server-side, but also used for local dev tools that never deploy to a server process long-term.

Node vs Deno/Bun?

Alternatives with different defaults; this course uses official Node.js LTS.

Do I need a browser to learn Node?

No—terminal and an editor are enough.

What comes next?

ES modules.