🚀 Node.Js Essentials as Backend Runtime Environment

🎯 Purpose

• Javascript (JS) a programming language initially created to add dynamic & interactive features to static web pages. Build to run in browsers.
• Node.js is a JS runtime built on Chrome’s V8 engine for running JS code server-side.
• NVM (Node Version Manager) allows easy installation, switching, and management of multiple Node.js versions.

🌱 Origin

• Brendan Eich created JavaScript in 1995 for Netscape Communications. The name was probabely a marketing tactic by Netscape to leverage the popularity of the Java, despite the two being unrelated.
• Node.js was created by Ryan Dahl in 2009, named for its modular “nodes” of functionality.
• NVM was created by Tim Caswell in 2010, with the name directly describing its purpose: managing Node versions.

🧠 Essentials

⚙️ Linux Installation

# Install NVM - Use installation guide versions https://github.com/nvm-sh/nvm
wget -qO- https://raw.githubusercontent.com/nvm-sh/nvm/v0.40.3/install.sh | bash
# Reload shell
exec $SHELL
# Verify NVM version:
nvm -v

# Install Node.js (LTS)
nvm install --lts

# Verify Node & NPM version
node -v
npm -v 

🛠 Useful NVM Commands

• nvm ls → List installed Node versions
• nvm ls-remote → List available Node versions
• nvm current → Show active version
• nvm use 20 → Switch to Node version 18
• nvm alias default 22 → Set default Node version
• nvm uninstall <version> → Remove a version
• To uninstall NVM & all Node.js versions on Ubuntu (double check and be carefull):

# Remove NVM directory containing all Node versions
rm -rf "$NVM_DIR"
# Find out current user´s shell
echo $SHELL
# Remove NVM environment references from user´s shell config (e.g. bash)
sed -i '/NVM_DIR/d' ~/.bashrc
# Remove any leftover Node binaries from PATH
sudo rm -rf /usr/local/{lib/node_modules,bin/node,bin/npm,bin/npx}
# Reload shell
exec $SHELL

📦 Package Manager

• NPM official website: npmjs.comZ
• NPM: is the default build-in Node.Js Package Manager used to install, manage, and share JavaScript libraries and tools.
• Init Project: npm init -y
• package.json
  • Project’s manifest file, listing its details and dependencies.
  • Example: { "dependencies": { "express": "^4.18.2" } }
  • Dependency version ranges using standard SemVer (MAJOR.MINOR.PATCH)
    • Caret (^): latest minor/patch >= version
    • Tilde (~): latest patch >= version
    • Exact (no special character): exact version
• package-lock.json
  • Locks exact versions of all dependencies to ensure consistent installations across different environments.
  • Example: It guarantees express is version 4.18.2 no matter what.
• node_modules folder
  • Holds all the actual code for project’s dependencies.
  • Example: It contains the express folder with all the framework’s files.
• Install Package: npm install <pkg> (local), npm install -g <pkg> (global)
• Remove Package: npm uninstall <pkg>
• List Packages: npm list --depth=0 (local), npm list -g --depth=0 (global)
• Run Scripts: npm run <script> (from package.json)
• Audit & Fix: npm audit → npm audit fix
• Check outdated packages: npm outdated
• Update to safe versions: npm update

Express

• Express Web Framework: expressjs.com
• Unopinionated (no rigid rules on usage), minimal and fast web framework for Node.js
• Provides tools and functions to manage server setup, HTTP Requests/Routing …

CORS - Cross-Origin Resource Sharing

• CORS Overview
• CORS: Security feature in web browsers controling whether a website can request resources from different domains.
• Blocking: Website at site-A.com trying to access data from an API at api-B.com would be blocked by default without CORS.
• Allow Access: To allow access, server needs to send a special header Access-Control-Allow-Origin back to the browser.
  → can be done with Node.js/Express and app.use(cors());

NodeMon Utility

• Nodemon website: nodemon.io
• Live reload Node.Js app on changes

🏃 Running Apps

node app.js         # Run JS script "app.js"
node -e "js code"   # Run JS Code in terminal
npm run start       # Run script "start" defined in package.json