Preλude-js

A modular implementation of Haskell's Prelude for modern JavaScript.

It ships as native ESM, runs on Bun or Node 20+, and keeps the runtime source in src/ without a generated CommonJS dist in the repo.

Why

• Small, composable helpers that feel close to Prelude semantics.
• Direct module and deep-function exports for focused imports.
• Bun-first tooling for install, test, docs, and generator workflows.

Install

bun add preludejs

npm install preludejs

Usage

import { List, Func, General } from 'preludejs'
import map from 'preludejs/List/map'

List.length([1, 2, 3]) // 3
List.elem(2, [1, 2, 3]) // true
Func.const('left', 'right') // 'left'
General.snd(['first', 'second']) // 'second'
map((x) => x * 2, [1, 2, 3]) // [2, 4, 6]

Develop

bun install
bun run check
bun run docs

Layout

• preludejs resolves to src/index.js.
• preludejs exposes named module namespaces like List, Func, Obj, and friends.
• preludejs/List, preludejs/Func, preludejs/Obj, and the other module subpaths are exported directly.
• Deep imports such as preludejs/List/map are also exported for consumers that want single-function entrypoints.
• Legacy generated module folders are not stored in the repository root.

See docs/README.md for the module reference.