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Node.js

Node.js is a cross-platform, open-source JavaScript runtime environment that executes JavaScript code outside of a web browser. Built on the V8 engine (from Chrome), Node.js enables server-side scripting, command-line tools, and scalable network applications.

🛠️ Installation & Version Management​

  • Official Downloads: nodejs.org/en/download
  • Version Manager: NVM (Node Version Manager) is the recommended way to install and manage multiple Node.js versions.
# Install NVM (Linux/macOS)
curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.7/install.sh | bash

# Install Node.js version 18
nvm install 18

# Use Node.js version 18
nvm use 18

# List installed versions
nvm ls

# Set default version
nvm alias default 18

Installation Paths:

  • Linux/macOS (NVM):
    Node binaries: ~/.nvm/versions/node/<version>/bin/node
    Global npm modules: ~/.nvm/versions/node/<version>/lib/node_modules/
  • System-wide (apt, brew, pkg):
    Node: /usr/bin/node or /usr/local/bin/node
    npm: /usr/bin/npm or /usr/local/bin/npm

📦 Package Managers​

npm​

  • npm is the default package manager for Node.js.
  • Installs dependencies, manages scripts, handles versioning, and publishes packages.
npm init                # Create a new package.json
npm install <pkg>       # Install a package locally
npm install -g <pkg>    # Install a package globally
npm run <script>        # Run a script from package.json
npm update              # Update dependencies
npm uninstall <pkg>     # Remove a package
npm list -g --depth=0   # List globally installed packages

Global modules path:

  • Linux/macOS: /usr/local/lib/node_modules/ or ~/.nvm/versions/node/<version>/lib/node_modules/
  • macOS (Homebrew): /opt/homebrew/lib/node_modules/

pnpm​

  • pnpm is a fast, disk space-efficient alternative to npm and yarn.
  • Uses a content-addressable store for node_modules, enabling faster installs and deduplication.
npm install -g pnpm         # Install pnpm globally
pnpm install                # Install dependencies
pnpm add <pkg>              # Add a package
pnpm remove <pkg>           # Remove a package
pnpm run <script>           # Run a script

npx​

  • npx runs Node binaries from npm packages without installing them globally.
npx create-react-app myapp      # Run a package binary temporarily
npx eslint .                    # Run eslint without global install

⚙️ Node.js CLI & Environment​

node -v                         # Show Node.js version
npm -v                          # Show npm version
which node                      # Show Node.js binary path
which npm                       # Show npm binary path
node script.js                  # Run a Node.js script
NODE_ENV=production node app.js # Set environment variable
  • REPL: Run node with no arguments for an interactive shell.
  • Environment Variables: Use .env files with dotenv or set variables inline.

📂 Project Structure & Files​

  • package.json — Project metadata, dependencies, scripts.
  • node_modules/ — Installed packages.
  • package-lock.json or pnpm-lock.yaml — Dependency lock files.
  • .npmrc — npm configuration file (registry, proxy, etc.).

🔍 Useful Node.js Commands​

npm outdated                    # Check for outdated dependencies
npm audit                       # Security audit of dependencies
npm ci                          # Clean install from lockfile
npm cache clean --force         # Clear npm cache
pnpm prune                      # Remove extraneous packages

🧩 Node.js Internals & Technical Details​

  • Single-threaded Event Loop: Node.js uses a non-blocking, event-driven architecture for high concurrency.
  • Native Addons: Write C/C++ modules using node-gyp.
  • Built-in Modules: fs, http, crypto, os, path, etc.
  • CommonJS & ES Modules: Supports both require() and import syntax.
  • Process Management: Use pm2 or forever for production deployments.

📚 Useful Links​