stopcock

A handful of functional TypeScript packages that play nicely together. Pipeable utilities covering arrays, dates, async tasks, state management, diffing, and image processing, with more to come.

import { pipe, A } from '@stopcock/fp'

const top10 = pipe(
  users,
  A.filter(u => u.active),
  A.map(u => ({ name: u.name, score: u.score })),
  A.take(10),
)

import { pipe } from '@stopcock/fp'
import { create, add, format } from '@stopcock/date'

const nextWeek = pipe(
  create.now(),
  add('days', 7),
  format('yyyy-MM-dd'),
)

import { pipe } from '@stopcock/fp'
import { fromPromise, map, flatMap, retry, timeout, run } from '@stopcock/async'

const fetchUser = pipe(
  fromPromise(() => fetch('/api/user')),
  flatMap(res => fromPromise(() => res.json())),
  map(data => data.name),
  retry({ attempts: 3 }),
  timeout(5000),
)

const name = await run(fetchUser)

import { diff, apply, invert } from '@stopcock/diff'

const patch = diff(
  { user: 'Tom', scores: [10, 20] },
  { user: 'Tom', scores: [10, 20, 30] },
)
const restored = apply(patch.target, invert(patch))

import { create, history } from '@stopcock/state'

const store = create({ count: 0, name: 'Tom' })
store.subscribe(s => s.count, (next) => console.log(next))
store.set(s => s.count, 1)

import { pipe } from '@stopcock/fp'
import { fromRGBA, resize, sharpen, contrast } from '@stopcock/img'

const thumbnail = (data: Uint8ClampedArray, w: number, h: number) => pipe(
  fromRGBA(data, w, h),
  resize(200, 200),
  sharpen,
  contrast(30),
)

---

@stopcock/fp Pipe, Option, Result, Array, String, lenses, and Stream. The core everything else builds on. @stopcock/date Date arithmetic, formatting, parsing, timezones, and business day logic. @stopcock/async Lazy Task type with retry, timeout, concurrency limits, and cancellation via AbortSignal. @stopcock/http Typed HTTP client with retry, timeout, dedup, and Task integration. @stopcock/img Pixel-level image processing. Filters, convolution, resize, crop. @stopcock/diff Structural diffing, patching, composition, and rebasing for objects and arrays. @stopcock/state Reactive stores with fine-grained subscriptions, middleware, undo/redo, and devtools.

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Array pipelines fuse automatically

pipe detects chainable array operations and fuses them into a single loop. take(10) bails after 10 hits. On a million-element array, that’s dozens of items touched instead of three full passes.

9xfilter→map→take(10) on 100K elements

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bun add @stopcock/fp