# cujojs/when

A solid, fast Promises/A+ and when() implementation, plus other async goodies.

Repository: https://github.com/cujojs/when
Canonical: https://ross.abutalabs.com/products/when
Language: JavaScript
License: NOASSERTION
License Family: other
Last push: 2022-04-10T19:35:16+00:00

## Health v2 (maintenance only)
Score: 23/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 0, release rhythm 8, longevity 100
- inputs: {"age_days": 5635, "days_push": 1606, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: no_license
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 3422, forks 383 (observed 2026-08-28T04:08:03.823324+00:00)

## What it is
When.js is a Promises/A+ compliant promise library for JavaScript with an ES6 Promise shim and rich async utilities like parallel/sequential task execution, promise mapping/reduction, and Node callback conversion. It is a standalone component of the cujoJS architectural toolkit.

## Use cases
- manage nested callback flows with promises
- run async tasks in parallel or sequentially
- convert node-style callback APIs to promises
- resolve arrays and hashes of promises
- shim ES6 Promise in older environments

## When to choose
- you need a battle-tested Promises/A+ implementation for legacy JS environments
- you want rich async combinators like map, reduce, and parallel task execution
- you need an ES6 Promise shim with debugging-friendly promises

## When to avoid
- you are targeting modern JavaScript with native Promises and async/await
- you want an actively developed library with frequent updates

## Facets
- artifact type: library
- maturity: maintenance
- function: concurrency, developer-tools
- domain: developer-tools, web-development
- platform: browser, cross-platform
- tags: promises, async, promises-aplus, es6-promise-shim, deferreds, javascript, nodejs

## Member repositories
- cujojs/when (main) score 23

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:08:03.823324+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 2026-08-29T18:38:08.255766+00:00, confidence not recorded.
  - readme: https://github.com/cujojs/when (fetched 2026-08-28T04:08:03.823324+00:00, sha 0623af1bf376)
  - registry_npm: https://registry.npmjs.org/when (fetched 2026-08-29T09:32:15.411334+00:00, sha 2b61df4fd918)
- Data as of 2026-08-30T08:39:29.467469+00:00.