# dtao/lazy.js

Like Underscore, but lazier

Repository: https://github.com/dtao/lazy.js
Canonical: https://ross.abutalabs.com/products/lazyjs
Homepage: http://danieltao.com/lazy.js/
Language: JavaScript
License: MIT
License Family: permissive
Last push: 2020-07-15T20:12:33+00:00

## Health v2 (maintenance only)
Score: 32/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 0, release rhythm 35, longevity 100
- inputs: {"age_days": 4863, "days_push": 2240, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: no_releases
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 5966, forks 258 (observed 2026-08-28T04:09:33.815474+00:00)

## What it is
Lazy.js is a functional utility library for JavaScript, similar to Underscore and Lodash, but built on a lazy evaluation engine that avoids creating intermediate arrays. It supports chaining map/filter/reduce-style operations over arrays, objects, strings, and async sequences with minimal work.

## Use cases
- process large arrays without creating intermediate arrays
- chain map/filter/take operations efficiently
- search-as-you-type over big datasets with early termination
- replace Underscore/Lodash for performance-critical iteration
- iterate over strings and objects lazily
- asynchronous sequence iteration

## When to choose
- you need Underscore/Lodash-style chaining but with better performance on large collections
- you want lazy evaluation with early exit (take, find) to avoid unnecessary computation
- you need a dependency-free functional utility library

## When to avoid
- you need a actively maintained library with modern ES support - last release was 2020
- your datasets are small and Lodash performance is sufficient
- you need async iteration features beyond basic AsyncSequence support

## Facets
- artifact type: library
- maturity: maintenance
- function: serialization, developer-tools
- domain: developer-tools, performance
- platform: browser, cross-platform
- tags: lazy-evaluation, functional-programming, underscore-alternative, lodash-alternative, sequences, algorithms, nodejs

## Member repositories
- dtao/lazy.js (main) score 32

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:09:33.815474+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 2026-08-29T17:50:09.971614+00:00, confidence not recorded.
  - readme: https://github.com/dtao/lazy.js (fetched 2026-08-28T04:09:33.815474+00:00, sha 65adc36a63a3)
  - homepage: http://danieltao.com/lazy.js/ (fetched 2026-08-29T08:46:16.549986+00:00, sha e36e6f464937)
  - site_page: http://danieltao.com/lazy.js/docs (fetched 2026-08-29T08:46:16.554912+00:00, sha b0d443e1beeb)
  - registry_npm: https://registry.npmjs.org/lazy.js (fetched 2026-08-29T08:46:16.558154+00:00, sha 49439abe9a70)
- Data as of 2026-08-30T08:39:29.467469+00:00.