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JavaScript

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

Browse 23 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

23 articles

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 What Is Node.js? A clear introduction to Node.js — the V8 engine, the event loop, non-blocking I/O, the npm ecosystem, and when Node is the right runtime for your project.
  17. 17 ES Modules Named exports, default exports, re-exports, dynamic import, and what actually makes a file a module — the modern JavaScript module system explained.
  18. 18 Closures A practical guide to JavaScript closures, lexical scope, the classic loop bug, and the patterns that make closures genuinely useful in production code.
  19. 19 DOM A modern guide to vanilla DOM manipulation: query selectors, creating and inserting nodes, event handling, delegation, and when a framework is actually worth it.
  20. 20 Event loop Build an accurate mental model of the JavaScript event loop, the call stack, web APIs, the task and microtask queues, and why setTimeout zero is not really zero.
  21. 21 Fetch API A practical guide to the Fetch API: GET and POST requests, JSON, headers, error handling, AbortController, and the 4xx/5xx rejection gotcha that bites everyone.
  22. 22 Prototypes Understand the JavaScript prototype chain, how Object.create works, what class syntax desugars to, and why this still matters in modern code.
  23. 23 this & binding Demystify the JavaScript this keyword with clear rules, arrow vs normal functions, bind/call/apply, class methods, and the bugs that catch every developer.