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JavaScript

The language of the web. Fundamentals, modern features, and patterns.

Browse 61 tutorials → Other topics

Why learn JavaScript?

  • The only language that runs natively in every browser.

  • Now runs everywhere — servers (Node, Bun, Deno), mobile (React Native), desktop (Electron), edge.

  • You cannot build an interactive web frontend without it.

  • Modern JS (ES2020+) is genuinely pleasant to write.

What you can build with JavaScript

Interactive web frontends Backend APIs with Node.js Cross-platform apps and tooling Browser extensions and serverless functions

JavaScript tutorials

61 articles · page 1 of 4

Hand-written tutorials, ordered as a recommended learning path.

  1. 01 What is JavaScript? A clear, professional introduction to JavaScript — what it is, how it runs in browsers and on servers, why it became the most-used language on Earth, and what you can build with it.
  2. 02 Setup & First Program Run JavaScript in your browser's console, install Node.js, set up VS Code, and write three working first programs — all in under fifteen minutes.
  3. 03 Variables (let, const, var) A practical guide to declaring variables in modern JavaScript — when to use const, when to use let, why var still exists, and the naming rules that keep your code readable.
  4. 04 Data Types Every JavaScript data type explained — strings, numbers, booleans, null, undefined, symbols, bigints, and objects — with practical examples and how to check types correctly.
  5. 05 Numbers & Math A complete beginner's guide to numbers in JavaScript — arithmetic, the Math object, rounding, formatting, NaN, Infinity, and the floating-point quirk every developer must know.
  6. 06 Strings A practical guide to JavaScript strings — template literals, indexing, the essential methods, immutability, and the modern ways to slice, search, and transform text.
  7. 07 Arrays A complete beginner's guide to JavaScript arrays — creation, indexing, the essential mutation methods, iteration, map/filter/reduce, and a first look at spread and destructuring.
  8. 08 Objects A practical guide to JavaScript objects — creation, access, mutation, iteration, shorthand syntax, destructuring, spread, and how object references actually work.
  9. 09 Operators & Comparisons A complete beginner's guide to JavaScript operators — arithmetic, comparison, logical, assignment, and the modern nullish coalescing and optional chaining operators.
  10. 10 Conditionals & Loops A complete beginner's guide to control flow in JavaScript — if/else, switch, for, while, for...of, break and continue, and the loops you should reach for first.
  11. 11 Functions A practical guide to JavaScript functions — declarations vs expressions, hoisting, parameters and arguments, default and rest parameters, return values, and functions as first-class values.
  12. 12 Arrow Functions A practical guide to arrow functions — concise syntax, implicit returns, and the lexical this that makes them perfect for callbacks but wrong for methods and constructors.
  13. 13 Destructuring & Spread A complete tour of the ES6 patterns that show up everywhere — object and array destructuring with defaults and renaming, the rest pattern, and spread for copies and merges.
  14. 14 Promises A practical guide to JavaScript promises — states, then/catch/finally, chaining, Promise.all, race, and allSettled, and how to escape the pyramid of doom.
  15. 15 async / await A practical guide to async functions and await — writing asynchronous code that reads like synchronous code, handling errors with try/catch, and running work in parallel.
  16. 16 ES Modules Named exports, default exports, re-exports, dynamic import, and what actually makes a file a module — the modern JavaScript module system explained.
  17. 17 Event Loop Explained Understand how the JavaScript event loop handles async operations including the call stack, microtasks, macrotasks, and execution order with practical examples.
  18. 18 structuredClone Learn how to use JavaScript structuredClone for deep copying objects, when it beats JSON.parse(JSON.stringify()), and what types it supports and cannot handle.
  19. 19 Design Patterns Learn the most useful JavaScript design patterns with practical examples including Singleton, Observer, Factory, Strategy, and more for cleaner code.
  20. 20 Memory Leaks Learn how to detect, diagnose, and fix JavaScript memory leaks using Chrome DevTools heap snapshots, allocation timelines, and common leak patterns.