// the find
leonardomso/33-js-concepts
📜 33 JavaScript concepts every developer should know.
A structured reference guide covering 33 (now many more) core JavaScript concepts, each with a dedicated page on a companion docs site. Originally a link collection, it has evolved into written explanations with code examples. Best suited for developers who want a map of what to learn rather than a book to read cover to cover.
The concept selection is genuinely good — it covers the things that actually trip people up (event loop, prototype chain, type coercion, closures) rather than just syntax. The test suite per concept is a nice touch: runnable examples that verify the described behavior rather than just prose you have to take on faith. The 'Beyond 33' extension adds browser APIs (Intersection Observer, WeakMap, Proxy) that most similar guides skip. The companion site structure means each concept gets its own URL, making it easy to link someone to exactly the thing they're confused about.
The original repo was a curated link list; that content has been replaced by the docs site, so the GitHub repo itself is now mostly a shell — the actual value lives on an external domain you don't control. No coverage of TypeScript, which is how most teams actually write JavaScript in 2026. The 'clean code' and 'design patterns' pages are dangerous at this level — pattern names without strong judgment about when NOT to use them tend to produce over-engineered junior code. Test coverage is uneven; some concepts have thorough tests while others (design-patterns, clean-code) are essentially untestable prose.