JavaScript

The programming language of the web.

JavaScript is taught here in 14 lessons, running from JavaScript basics through to Tooling: linting, formatting, bundling and testing. Each lesson takes one topic, shows the working code, and links onward to the next, so the course can be read straight through in order.

Lessons

1. JavaScript basicsVariables, the seven primitives, type coercion, and the == vs === decision that causes most beginner bugs.
2. Functions and scopeParameters, defaults, arrow functions, closures and this — the ideas behind almost every JavaScript interview question.
3. Arrays and iterationThe methods that replace most for-loops — map, filter, reduce, find — and when mutation versus copying matters.
4. Objects and destructuringProperty shorthand, spread merging, optional chaining, and copying objects without the reference traps.
5. Working with the DOMSelecting elements, reading and writing content safely, creating nodes, and why innerHTML deserves caution.
6. EventsaddEventListener, bubbling and capturing, delegation for dynamic lists, and forms without page reloads.
7. Async JavaScript and fetchPromises, async/await, real fetch usage with error handling, cancellation, and running tasks concurrently.
8. Classes, prototypes and object-oriented patternsThe prototype chain, class syntax, private fields, static members, getters and setters, and when composition beats inheritance.
9. Modules and project structureES module import and export, default versus named exports, dynamic import, CommonJS interop, folder layout and the package.json fields that matter.
10. Errors, exceptions and defensive codethrow and Error subclasses, try/catch/finally, how errors propagate through async code, custom error shapes and a practical debugging strategy.
11. Iterators, generators, Map and SetSymbol.iterator, generator functions and yield, lazy sequences, for...of, when a Map beats an object, and the Set operations you actually need.
12. The event loop, timers and concurrencyThe call stack, macrotasks versus microtasks, setTimeout and setInterval, requestAnimationFrame, starvation, and chunking long work.
13. Numbers, dates and internationalisationFloating-point precision, BigInt, the Math helpers worth knowing, Date pitfalls with UTC, and Intl formatting for numbers, dates and relative time.
14. Tooling: linting, formatting, bundling and testingESLint and Prettier, a Vite dev and build workflow, type checking JavaScript with JSDoc, Vitest basics and wiring it all into npm scripts and CI.

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Last refreshed 2026-09-18.