node_02 - Getting Started with Node¶

Three ways to install Node and two of them are wrong for production
You can download the official installer from nodejs.org , use your package manager (apt , brew , yum) , or use nvm (Node Version Manager). The first two lock you into a single Node version managed by someone else's release schedule. NVM lets you switch versions per-project , which is non-negotiable when you maintain multiple apps on different Node releases

installation - do it right¶

nvm (recommended) - installs per-user , switches versions per-shell , doesn't touch system packages

# Install nvm
curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.40.0/install.sh | bash

# Restart terminal or source your profile
source ~/.bashrc

# Install the latest LTS version
nvm install --lts

# Use it
nvm use --lts

# Set as default
nvm alias default 'lts/*'

Package manager - convenient but lags behind releases

# Ubuntu/Debian
sudo apt update && sudo apt install nodejs npm

# macOS (Homebrew)
brew install node

Official installer - fine for desktops , annoying for automation

Download the LTS version from nodejs.org and run the installer. It adds node and npm to your PATH globally

verify the install¶

node --version
# v22.14.0  (or whatever LTS is current in your timeline)

npm --version
# v10.x.x

If these don't return version numbers , something went wrong. Check your PATH variable and make sure the nvm directory is sourced in your shell profile

write and run your first script¶

Create a file called app.js with this content:

// app.js - your first Node script
console.log('Hello from Node.js')
console.log('Running version:' , process.version)
console.log('Platform:' , process.platform)

Run it:

node app.js
# Hello from Node.js
# Running version: v22.14.0
# Platform: linux

That's it. That's the whole pipeline. Node reads the file , V8 compiles it , and executes it. No HTML page needed , no browser required

the REPL¶

Type node in your terminal with no arguments and you drop into a Read-Eval-Print Loop. It's a live JavaScript playground where you can test code before putting it in a file

$ node
> console.log('testing in repl')
testing in repl
undefined
> const x = 5 + 3
undefined
> x
8
> .exit

Type .exit or press Ctrl-D twice to leave. The REPL is great for testing small snippets but terrible for anything that needs to persist - closes your session and everything is gone

hello world as an HTTP server¶

The classic Node hello world is an HTTP server. This is the minimum viable web server:

// hello-world.js
const http = require('http')

const hostname = '127.0.0.1'
const port = 3000

const server = http.createServer((req , res) => {
  res.statusCode = 200
  res.setHeader('Content-Type' , 'text/plain')
  res.end('Hello World\n')
})

server.listen(port , hostname , () => {
  console.log(`Server running at http://${hostname}:${port}/`)
})

Run it with node hello-world.js and open http://127.0.0.1:3000 in your browser. You'll see "Hello World". Ctrl-C stops the server

Security note: This server has no routing , no input validation , no rate limiting , no CORS handling , no security headers. It's a teaching example , not a production deployment. Every request hits the same callback and gets the same response. Real servers need more

common pitfalls¶

Port already in use - EADDRINUSE means something is already listening on port 3000. Use a different port or kill the other process

# Find what's on port 3000
lsof -i :3000
# Kill it
kill -9 <PID>

Wrong file path - Node throws MODULE_NOT_FOUND or ENOENT if the file doesn't exist. Use absolute paths or verify the relative path from your current working directory

# Check current directory
pwd
# List files
ls
# Run with explicit path
node ./app.js

Permissions - if you installed Node globally with a package manager , you might need sudo for global npm installs. NVM installs to your home directory and avoids this entirely

prerequisites¶

node_01 - Node Introduction

next -> node_03_js_requirements.md