Hyperjump - Pact

Higher-order functions for iterators and async iterators. Each function is a step you put in a pipe. A pipeline does its work one value at a time, and only when a value is asked for.

Read the documentation at hyperjump.io

npm install @hyperjump/pact

import * as Pact from "@hyperjump/pact";

const numbers = new Set([1, 2, 3, 4, 5, 6, 7, 8, 9]);

Pact.pipe(
  numbers,
  Pact.filter((n) => n % 2 === 0),
  Pact.map((n) => n * 2),
  Pact.take(3),
  Pact.toArray
); // [4, 8, 12]

The pipeline reads the Set directly, without making arrays in between steps, and take(3) stops it at 6. Array methods would copy the Set into an array first, and then filter and map all of it.

• Composable. Steps are plain functions. Use compose to build a pipeline without a source, then use it with as many sources as you like.
• The platform's names. map, filter, take, flatMap, toArray, and the rest work like the native Iterator helpers. pact adds what the helpers don't have, like scan, takeWhile, zip, and toObject.
• Sync and async. @hyperjump/pact/async has the same functions for async iterables. Its callbacks can return promises.
• Closes what it opens. When a pipeline stops early, it closes the iterators it was reading. A generator's finally block runs.
• Small and fast. No dependencies. TypeScript types included. Works in Node.js 24 or later and browsers.

Documentation

The documentation is at hyperjump.io/pact.

• Install: Node.js, browsers, and TypeScript
• Pipelines: pipe, compose, and what a step is
• Transforming: map, filter, take, and the other steps
• Sources: range, concat, zip, and zipKeyed
• Collecting: toArray, reduce, find, and the other functions that end a pipeline
• Async: async iterables, async callbacks, and mixing them with sync ones
• Benchmarks: pipelines compared with array methods
• Migrating from v1: what changed, and what to do about it

Using v1? See the v1 README.

Contributing

See design/ for how it works and why. The documentation's source is in website/.

npm install
npm test               # Run the tests
npm test -- --watch    # Run the tests when files change
npm run lint
npm run type-check
npm run check-website  # Check the examples in website/

License

MIT