JavaScript
Make web pages interactive
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read 9 chapters Programming language
Created
1995 by Brendan Eich at Netscape
Type
Dynamic, interpreted (JIT-compiled)
Runs in
Every browser + Node.js / Deno / Bun
Standard
ECMAScript (ES2024)
Powers
98% of all websites (client-side)
npm packages
2.5M+ (largest ecosystem)
File extension
.js / .mjs
Best for
Web apps, APIs, serverless functions
What is JavaScript?
JavaScript is the programming language of the web. It runs in every browser natively, and with Node.js, Deno, and Bun it also runs on servers. It's the only language that runs client-side in all browsers.
Why JavaScript?
| Feature | JavaScript | TypeScript | Python |
|---|---|---|---|
| Runs in browser | ✅ Native | ✅ (compiles to JS) | ❌ |
| Learning curve | Easy | Medium | Easy |
| Type safety | Dynamic | Static | Dynamic |
| npm packages | 2.5M+ | Uses npm | pip packages |
| Best for | Web, APIs | Large web projects | Data science, scripting |
What you'll learn
| Chapter | What you'll know |
|---|---|
| Introduction | What JavaScript is, how it runs |
| Syntax | Variables, types, functions |
| DOM | Manipulating web pages |
| Async | Promises, async/await, fetch |
Start with introduction.