You Don't Know JS

You Don’t Know JS is a book series that explores the core mechanisms of the JavaScript language.

github.com/getify/You-Dont-Know-JS
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About You Don't Know JS

You Don't Know JS is a book series that explores the core mechanisms of the JavaScript language. This GitHub repository hosts the second edition, which the author describes as a deep examination of how the language works. The series' preface explains the motivation and perspective behind the books.

The author states that the books can be read online for free. The second edition is self-published through GetiPub, and published copies are sold through Leanpub and Amazon. Two titles are marked as canceled and two are marked as drafts, so not every planned book is complete. The series is described as complete and is not accepting further contributions. The materials are licensed under Creative Commons Attribution-NonCommercial-NoDerivs 4.0, which limits noncommercial reuse and prohibits derivative works.

Key features

  • Explains core JavaScript mechanisms in depth across a series of books
  • Includes Get Started and Scope & Closures in the second edition
  • Recommends a specific reading order for the second edition titles
  • Free online reading of the books, as stated by the author
  • Published books available for purchase through Leanpub and Amazon
  • Includes The Unbooks, an ebook in the series
Best for: Developers who want a deeper understanding of how core JavaScript mechanisms work, beyond introductory material.
Good for
  • The books can be read online for free, according to the author
  • Gives a recommended reading order for the second edition titles
  • Covers core language mechanisms in depth
Watch out for
  • Sync & Async and ES.Next & Beyond are marked as canceled
  • Objects & Classes is a draft stable and Types & Grammar is a rough draft
  • Licensed under CC BY-NC-ND 4.0, which restricts noncommercial reuse and prohibits derivative works

You Don't Know JS at a glance

Type
Open-source project
Pricing
Not confirmed. Check the site
Open source
Not stated
Language
English
Last checked
Oct 6, 2026 · Online when checked
Listed
Oct 5, 2026

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You Don't Know JS FAQ

Can I read the books for free?
The author states that the books can be read online entirely for free. Published copies are also sold through Leanpub and Amazon.
Is the series still accepting contributions?
No. The series is described as complete and is not open to further contributions.
Are all the planned titles finished?
No. Sync & Async and ES.Next & Beyond are marked as canceled, and Objects & Classes and Types & Grammar are marked as draft versions.
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