# @fxts/core > A functional library for TypeScript/JavaScript programmers. Latest version **2.0.1** (published 2026-08-08) · Apache-2.0 license · 0 weekly downloads ## Install ```sh npm install @fxts/core pnpm add @fxts/core yarn add @fxts/core bun add @fxts/core ``` ## Health **Score 75/100 (B)** — status: active. Positive: has types; esm support; no vulnerabilities; has provenance; recently updated; high maintenance score; high quality score. Warnings: low downloads. ## Facts | | | |---|---| | Version | 2.0.1 | | Published | 2026-08-08 | | First published | 2021-11-18 | | Weekly downloads | 0 | | License | Apache-2.0 | | TypeScript types | bundled | | Module format | ESM + CommonJS | | Node | >=10 | | Dependencies | 1 | | Unpacked size | 3.8 MB | | Known vulnerabilities | 0 | | Install scripts | no | | Provenance | attested (GitHub Actions) | | GitHub stars | 1168 | | Maintainers | marpple-dev-admin, dohyeong, xodltus | | Keywords | fp, lazy, concurrency | ## Links - npm: https://www.npmjs.com/package/@fxts/core - Repository: https://github.com/marpple/FxTS - Homepage: https://fxts.dev - Issues: https://github.com/marpple/FxTS/issues - npm.io page: https://npm.io/package/@fxts/core ## Dependencies (1) - [tslib](https://npm.io/package/tslib.md) ^2.6.0 ## Recent versions - 2.0.1 (latest) — 2026-08-08 - 2.0.0 — 2026-08-08 - 1.28.0 — 2026-08-08 - 1.26.0 — 2026-02-19 - 1.25.0 — 2026-02-01 - 1.24.0 — 2026-01-21 - 1.23.0 — 2025-12-29 - 1.22.0 — 2025-12-24 - 1.21.1 — 2025-11-26 - 1.21.0 — 2025-11-23 - 1.20.0 — 2025-11-15 - 1.19.0 — 2025-10-17 - 1.18.0 — 2025-10-13 - 1.17.0 — 2025-09-14 - 1.16.0 — 2025-09-09 - … 67 more at https://npm.io/package/@fxts/core/versions ## README FxTS Logo # FxTS [![Build Status](https://github.com/marpple/FxTS/actions/workflows/ci.yml/badge.svg)](https://github.com/marpple/FxTS/actions) [![npm version](https://badge.fury.io/js/@fxts%2Fcore.svg)](https://www.npmjs.com/package/@fxts/core) [![License](https://img.shields.io/badge/license-Apache%202.0-blue.svg)](./LICENSE) FxTS is a functional programming library for TypeScript. - Provides [lazy evaluation](https://fxts.dev/guide/lazy-evaluation) for memory-efficient data processing with functions like [pipe](https://fxts.dev/api/pipe), [map](https://fxts.dev/api/map), [filter](https://fxts.dev/api/filter), and [take](https://fxts.dev/api/take). - Handles [concurrent requests](https://fxts.dev/guide/handle-concurrency) efficiently with [concurrent](https://fxts.dev/guide/concurrent) and [toAsync](https://fxts.dev/api/toAsync). - Offers excellent TypeScript support with strong type inference. - Follows standard [iteration protocols](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols) (Iterable/AsyncIterable). ## Why FxTS? | | FxTS | lodash | Native (Array + [Iterator Helpers](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Iterator)) | | --------------------------------------------- | ---------------------------------------------------------- | ----------------- | ------------------------------------------------------------------------------------------------------------------------------ | | Lazy evaluation | ✅ | 🔶 `_.chain` only | ✅ ES2025 | | AsyncIterable pipelines | ✅ | ❌ | ❌ (proposal stage) | | Concurrency control with backpressure | ✅ [`concurrentPool`](https://fxts.dev/api/concurrentPool) | ❌ | ❌ | | Curried, data-last composition (`pipe`) | ✅ | 🔶 `lodash/fp` | ❌ | | Early termination across async work (`take`) | ✅ | ❌ | 🔶 sync only | | Literal-preserving inference (`Record<"a"…>`) | ✅ | ❌ | — | | Deep utils (`isEqual`, `cloneDeep`, `merge`) | ✅ | ✅ | ❌ | Migrating from `p-limit`/`p-map`? See the [migration guide](https://fxts.dev/guide/migrate-from-p-map). ## Installation ``` npm install @fxts/core ``` ## Usage Use `pipe` for function composition or `fx` for method chaining: ```ts import { each, filter, fx, map, pipe, range, take } from "@fxts/core"; pipe( range(10), map((a) => a + 10), filter((a) => a % 2 === 0), take(2), each((a) => console.log(a)), ); // chaining fx(range(10)) .map((a) => a + 10) .filter((a) => a % 2 === 0) .take(2) .each((a) => console.log(a)); ``` ## Usage (concurrent) Handle multiple async operations in parallel with `concurrent`: ```ts import { concurrent, countBy, flat, fx, map, pipe, toAsync } from "@fxts/core"; // maybe 1 seconds api const fetchWiki = (page: string) => fetch(`https://en.wikipedia.org/w/api.php?action=parse&page=${page}`); const countWords = async (concurrency: number) => pipe( ["html", "css", "javascript", "typescript"], toAsync, map(fetchWiki), map((res) => res.text()), map((words) => words.split(" ")), flat, concurrent(concurrency), countBy((word) => word), ); await countWords(); // 4 seconds await countWords(2); // 2 seconds ``` ## Documentation For more information, visit [fxts.dev](https://fxts.dev). For LLM-friendly documentation, see [llms.txt](https://fxts.dev/llms.txt). ## Contributing We welcome contributions from everyone in the community. Please read our [Contributing Guide](./CONTRIBUTING.md). ## License Apache License 2.0 © [Marpple](https://www.marpple.com). See [LICENSE](./LICENSE) for details. --- _Source: https://npm.io/package/@fxts/core · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._