You Don't Know JS Yet is a comprehensive book series focused on deep exploration of JavaScript's core mechanisms and language fundamentals. The repository hosts the second edition of this educational resource, which represents an 11-year journey of development and refinement. The series is designed to move beyond surface-level JavaScript knowledge and provide readers with thorough understanding of concepts that many developers overlook or misunderstand.
The second edition consists of multiple published and in-development titles available through various channels. The two completed books are Get Started and Scope & Closures, both available for purchase on Leanpub and Amazon. Additionally, The Unbooks collection includes Objects & Classes in draft stable form and Types & Grammar in rough draft status. Two titles, Sync & Async and ES.Next & Beyond, were canceled during development. The repository recommends reading the books in a specific order, beginning with Get Started to establish foundational knowledge before progressing to more advanced topics like scope and closures.
A distinctive feature of this repository is its commitment to free online access. All book content is available to read entirely free on the GitHub repository itself, while paid versions through retail channels support the author's ongoing work. The second edition is self-published through GetiPub publishing, representing a shift in distribution strategy from traditional publishing models. The author provides multiple financial contribution options including GitHub Sponsorship, Patreon, and PayPal for those who wish to support the project beyond purchasing published editions.
The repository demonstrates significant community engagement despite being closed to further contributions. GitGenius activity tracking shows 131 tracked issues and pull requests with a median response latency of 77,736 hours and mean latency of 60,608 hours. The most active labels relate to the second edition with 76 tracked items, followed by errata and editorial categories with 5 items each. The primary maintainer getify generated 129 tracked events, with secondary contributors StigNygaard and eulier1 contributing 5 and 4 events respectively. The repository's contributor network overlaps with major projects including Microsoft's VSCode and TypeScript repositories, as well as the Rust language repository, indicating its significance within the broader programming education ecosystem.
The series covers essential JavaScript topics including closures, prototypes, asynchronous programming, and ES2015/ES6 features. The repository is classified across multiple domains including JavaScript, Programming, Web Development, Language Fundamentals, Core Concepts, Advanced Topics, Deep Dive, Learning Guide, and Reference Material. Frontend Masters serves as the exclusive sponsor for the first two books of the second edition, and the author teaches all workshops exclusively through that platform. The materials are copyrighted 2019-2025 by Kyle Simpson and licensed under Creative Commons Attribution-NonCommercial-NoDerivs 4.0 Unported License, allowing free distribution and reading while restricting commercial use and modifications.
