# getify/You-Dont-Know-JS

A book series (2 published editions) on the JS language.

Repository: https://github.com/getify/You-Dont-Know-JS
Canonical: https://ross.abutalabs.com/products/you-dont-know-js
Homepage: https://www.amazon.com/dp/B085XXCJ7X
License: NOASSERTION
License Family: other
Topics: book-series, javascript, closures, prototypes, async, es6, es2015, training-materials, book, training-providers, education, programming, learn-to-code
Last push: 2026-02-15T04:36:44+00:00

## Health v2 (maintenance only)
Score: 62/100 (v2, computed 2026-09-03T02:39:23.370411+00:00)
- activity 67, release rhythm 35, longevity 100
- inputs: {"age_days": 4674, "days_push": 199, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: no_releases, no_license
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 184741, forks 33428 (observed 2026-08-28T04:12:28.342601+00:00)

## What it is
A free, open-source book series by Kyle Simpson diving deep into the core mechanisms of the JavaScript language, with two published editions. The second edition is complete and readable online, with purchasable ebook/print versions.

## Use cases
- learn javascript deeply
- understand closures and scope in js
- study javascript prototypes and this
- learn async javascript patterns
- free javascript books online
- prepare for javascript interviews

## When to choose
- you want a deep, mechanism-level understanding of JavaScript rather than framework tutorials
- you prefer free, self-paced reading material
- you are teaching or training developers on JS fundamentals

## When to avoid
- you need a quick reference or API documentation
- you want coverage of specific frameworks like React or Vue
- you need beginner-friendly interactive exercises instead of prose

## Facets
- artifact type: learning-resource
- maturity: stable
- function: documentation, developer-tools
- domain: programming-languages, tutorials, web-development, education
- platform: -
- tags: javascript, book-series, closures, prototypes, async, es6, free-online-books, web-server

## Member repositories
- getify/You-Dont-Know-JS (main) score 62

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:12:28.342601+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-29T16:10:43.725598+00:00, confidence not recorded.
  - readme: https://github.com/getify/You-Dont-Know-JS (fetched 2026-08-28T04:12:28.342601+00:00, sha 97fb91d01473)
  - homepage: https://www.amazon.com/dp/B085XXCJ7X (fetched 2026-08-28T17:23:19.036188+00:00, sha 6d1d7ac1af17)
- Data as of 2026-08-30T08:39:29.467469+00:00.