Lecture on Node.js Fundamentals

Introduction to Node.js

• Node.js is an open-source, cross-platform runtime environment for executing JavaScript code outside of a browser.
• Commonly used for building backend services (APIs) to power client applications (web or mobile apps).
• Node.js is ideal for highly scalable, data-intensive, and real-time backend services.

Advantages of Node.js

• Ease of Use: Simple to get started for prototyping and agile development.
• Performance: Can build super-fast and highly scalable services.
  • Example: PayPal's switch from Java and Spring to Node resulted in doubling requests per second and improving response times by 35%.
• JavaScript: Usage of JavaScript on both the front-end and back-end offers cleaner and more consistent code, allowing front-end developers to become full-stack developers.
• Ecosystem: Largest ecosystem of open-source libraries, offering pre-built components to accelerate development.

Node.js Architecture

• Runtime Environment: Executes JavaScript code outside the browser using the V8 engine, which converts JS code into machine code.
• JavaScript Engines: V8 engine (used in Chrome and Node.js), SpiderMonkey (Firefox), Chakra (Edge).
• Environment Objects: Unlike browsers that have window/document objects, Node.js provides different objects for working with the file system, network, etc.

Asynchronous Architecture

• Non-blocking: Node.js uses an asynchronous, non-blocking architecture.
  • Similar to a waiter in a restaurant taking multiple orders without waiting for one order to be completed.
  • Single thread handles multiple requests by delegating operations to the system (e.g., file system or database).
• Blocking Architecture: Traditional synchronous systems like ASP.NET or Rails use blocking architecture, leading to inefficient resource usage.
• Event Queue: Node.js uses an event queue to manage completed operations, making it more efficient for I/O-bound tasks.

Installing Node.js

• Check if Node.js is installed: node --version
• Download from nodejs.org: Choose the LTS version.
• Commonly used editors: VS Code, Sublime, Atom.
• Basic Usage: Create a JS file, define functions, and execute using the node app.js command.

Node.js Module System

• Modules: Every file in a Node app is considered a module; variables and functions are scoped to their file.
• Exporting Modules: Use module.exports to expose functions or variables outside the module.
• Loading Modules: Use require to load other modules.
• Core modules include fs, http, os, path, etc.

Example Modules

• Path Module: Provides utilities for working with file and directory paths.
  • Usage: const path = require('path');
• OS Module: Provides methods for getting information about the operating system.
  • Usage: const os = require('os');
• File System Module: Provides methods for interacting with the file system.
  • Usage: const fs = require('fs');

Event Emissions

• Event Emitter: Core of Node.js event-driven architecture.
• Creating and Handling Events: Use eventEmitter.on to handle events and eventEmitter.emit to raise events.
• Custom Events: Extend EventEmitter to create custom event-driven systems.

HTTP Module

• Building a Web Server:

  • Use http.createServer to create a basic web server.
  • Use the request and response objects to handle HTTP requests and responses.

  const http = require('http');
  const server = http.createServer((req, res) => {
    if (req.url === '/') {
      res.write('Hello World');
      res.end();
    } else if (req.url === '/api/courses') {
      res.write(JSON.stringify([1, 2, 3]));
      res.end();
    }
  });
  server.listen(3000);
  console.log('Listening on port 3000...');
  

Conclusion

• Node.js is powerful for creating scalable, efficient web applications using JavaScript across both the client and server.
• Emphasis on mastering the fundamentals and leveraging core modules.
• The ecosystem and community support make it a strong choice for modern web development.