What is Node.js?

Node.js is a powerful JavaScript runtime built on Chrome’s V8 JavaScript engine. It allows you to run JavaScript on the server side, enabling full-stack JavaScript development.

Key Concepts

Event-Driven Architecture

Node.js uses an event-driven, non-blocking I/O model that makes it lightweight and efficient.

graph TD
    A[Client Request] --> B[Event Loop]
    B --> C{Is Operation Async?}
    C -->|Yes| D[Delegate to Thread Pool]
    C -->|No| E[Execute Immediately]
    D --> F[Callback Queue]
    F --> B
    E --> G[Send Response]

Single-Threaded Event Loop

Despite being single-threaded for JavaScript execution, Node.js can handle many concurrent connections efficiently through its event loop mechanism.

Why Node.js?

Fast Performance: V8 engine compiles JavaScript to native machine code
NPM Ecosystem: Largest package registry with millions of reusable modules
Scalability: Non-blocking I/O perfect for I/O-intensive applications
Full-Stack JavaScript: Same language for frontend and backend

Installation

macOS/Linux

# Using nvm (recommended)
curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.0/install.sh | bash
nvm install --lts

Verify Installation

node --version
npm --version

Your First Node.js Program

Create a file hello.js:

console.log('Hello, Node.js!');
console.log('Node version:', process.version);
console.log('Platform:', process.platform);

Run it:

node hello.js

What JavaScript engine does Node.js use?

SpiderMonkey

JavaScriptCore

Chakra

What makes Node.js efficient for I/O operations?

Multi-threading

Non-blocking I/O

Compiled code

Memory caching

Which package manager comes with Node.js by default?

yarn

pnpm

npm

bower

Next Steps

In the next lesson, we’ll explore Node.js modules and the CommonJS module system.