33 JS Concepts
A reading guide to 33 core JavaScript concepts, with explanations and code examples.
- Stars
- 66.5k
- Forks
- 9.1k
- Licence
- MIT
- Language
- JavaScript
- Last update
- 15 days ago
- Type
- Learning resource
What it is
This repository is a curated list of 33 JavaScript concepts, from primitive types and closures to the event loop, Promises, and async/await. Each concept links to an explanation and examples on the project's companion website, 33jsconcepts.com. It is meant for developers who want to understand how the language works beneath everyday usage.
- Read through the Fundamentals section to understand primitive types, equality operators, and scope
- Study the Async JavaScript section to understand callbacks, Promises, and async/await
- Look up a specific concept such as Pure Functions or Recursion before a code review or interview
- Use the linked examples as a starting point for your own experiments
Great for
- Developers who know basic JavaScript and want to fill gaps in core concepts
- Students preparing for JavaScript interviews or courses
- Developers who want a structured reading order through fundamentals like scope, this, and the event loop
- Readers who prefer short explanations with links to deeper material
Not ideal for
- Complete beginners with no programming background, since the entries assume some familiarity with the language
- Readers looking for a hands-on project or interactive course, since the README points to a website for the content rather than exercises
- Anyone needing framework-specific guidance, since the topics are general JavaScript rather than React or Angular
How to get it
- 1
Read it online
Clone the repository
git clone https://github.com/leonardomso/33-js-concepts - 2
Run it
- Open https://33jsconcepts.com in your browser
- Choose a concept from the Fundamentals section
- Read the explanation and work through the code examples
- Move on to the next section when you are comfortable
- 3
Get the most out of it
- Read the Fundamentals section first, since later topics build on it
- Pair each concept with a small script in your own editor to test the examples
- Check TRANSLATIONS.md if you prefer reading in another language
Downloads
Strengths
- Covers a broad range of core topics in one organized list
- Each concept has a short summary describing what it covers
- Links to a full guide website with explanations and code examples
Trade-offs
- The README is truncated and only shows part of the concept list, so full coverage is not visible here
- Content lives mainly on an external website, so the repository itself is a table of contents rather than a complete tutorial
- Summaries are brief and do not show the depth of each explanation
How it compares
| Project | Stars | Type | Level | Updated | Best for |
|---|---|---|---|---|---|
| 33-js-concepts (this) | 66.5k | Learning resource | beginner | 15 days ago | Developers who know basic JavaScript and want to fill gaps in core concepts |
| modern-js-cheatsheet | 25.6k | Learning resource | beginner | 2.1 years ago | Developers with basic JavaScript who are starting to read React or other modern codebases |
| javascript-testing-best-practices | 24.6k | Learning resource | beginner | 2.4 years ago | Developers who already write some JavaScript tests and want to improve their structure |
| pytudes | 24.4k | Learning resource | intermediate | 8 days ago | Python learners who want practice problems with worked explanations |
| electron-vue | 15.3k | Learning resource | intermediate | 4.8 years ago | Developers who already know Vue and want to build a desktop app |
| javascript | 148k | Learning resource | beginner | 7 months ago | Teams that want one shared JavaScript style without debating every rule |
Stats synced from GitHub. The assessment above was drafted with AI from the project's README on 2026-10-29 and may miss recent changes — check the README before relying on a command. MIT licence: free to use, modify and distribute, including commercially, as long as you keep the copyright notice.