20. Node.js

BootCamp by Dr.Angela

1. What is Node.js?

• Node.js is a JavaScript runtime that allows you to run JavaScript outside the browser (on a server or local machine)
• Why use frameworks/libraries? : Reuse components, Reduce development overhead
  • ex) Reading files, writing files, URL Strings, Networking, Data Streams, Diagnostics, Tests, Debugger, Error Codes
• Definition : “Node.js is an asynchronous, event-driven JavaScript runtime designed to build scalable network applications.”
  • Key Concepts
  • JavaScript Runtime : Runs JS outside the browser (server/local computer)
  • Asynchronous : Executes tasks without blocking (non-blocking)
  • Event-driven : Responds to events (requests, user actions, etc.)
  • Application : On Server(Computer)
• Why Node.js? : Full-stack JavaScript, Scalable, Non-blocking I/O , Huge ecosystem

2. Using Node.js

• Check version : node -v
• REPL (Read-Eval-Print Loop) : node
  • Commands
  • .help : show commands)
  • .exit or Ctrl + C (twice) : exit
  • Similar to the browser console
• Run a JS file : cd path/to/file node index.js

3. Native Node Modules

• Native Modules : Built-in modules provided by Node.js
• File System (fs) : const fs = require("fs");
  • Write file : fs.writeFile("message.txt", "Hello from NodeJS!", (err) => { if (err) throw err; console.log("The file has been saved!"); });
  • Read file : fs.readFile("./message.txt", "utf8", (err, data) => { if (err) throw err; console.log(data); });
  • "utf8" → encoding option
• Docs : https://nodejs.org/docs/latest-v18.x/api/fs.html

4. NPM (Node Package Manager)

• A repository of packages and libraries
• Website : https://www.npmjs.com/
• Initialize project : npm init
  • Quick setup : npm init -y
• Install packages : npm install
  • ex) npm i sillyname
• Module Systems
  • CommonJS (CJS) : ex) const generateName = require("sillyname");
  • ES Modules (ESM) : ex) import generateName from "sillyname";
  • Enable ESM : "type": "module"
• Example : import superheroes, { randomSuperhero } from "superheroes";

const name = randomSuperhero();
console.log(`I am ${name}!`);

5. Mini Project: QR Code Generator

• Packages : inquirer(user input), qr-image(generate QR codes)

• Install : npm i inquirer qr-image

• Note : Be careful with package names (typos can install wrong packages), Always check package documentation