data

A reactive data engine. $(value) wraps an object or array into a live source; chainable operators (filter, between, gt/lt/gte/lte, az/za/top/limit/reverse, length, sum/avg/max/min, median/percentile/quantile, some/every, intersect/union/ except, group/distinct, map/to/reduce, tap, keys/values) derive incrementally-maintained views; subscriptions deliver consolidated per-commit deltas (native sink() batches by reference, v2-profile records via connect(), wire batches via wireSink()); a render layer binds views to the DOM (builders or JSX). Work is proportional to the change, not the data.

Live: https://pemrouz.github.io/data/ — the landing page runs this very engine in the browser (its source is site/).

Install

npm i data

import { $, batch, render, el, list } from 'data'

ESM only (no require entry). Node ≥ 20 imports it as is (no flags — the package ships JavaScript); a browser takes it through a bundler, or an importmap that points data at the package's dist/api/index.js. JSX: "jsxImportSource": "data" resolves the automatic runtime (data/jsx-runtime, data/jsx-dev-runtime); the classic h/Fragment/For/ErrorBoundary come off the main entry, typed per tag as well ("jsx": "react", "jsxFactory": "h", "jsxFragmentFactory": "Fragment"). TypeScript resolves the subpaths' types under moduleResolution node16/nodenext/bundler (the legacy node10 sees only data). data/devtools is the inspector — importing it attaches $.inspect/$.graph/ $.trace/… and, in a browser, mounts the overlay panel (?nopanel keeps the console helpers only); inspect/graph/trace/profile/cascades/ mountPanel are its named exports; runtime().seq / .onCommit(hook) / .graph() are the observability primitives the shipped Runtime type carries.

The tarball is dist/ — the sources type-stripped FILE-FOR-FILE by build.mjs (Node's stripTypeScriptTypes: one module per source file, .ts specifiers rewritten to .js, nothing bundled, so a stack trace names the file you would open) — plus the curated types (types/public.d.ts for data, types/jsx-runtime.d.ts for data/jsx-runtime + data/jsx-dev-runtime, types/devtools.d.ts for data/devtools: written by hand and gated by npm run typecheck, not emitted) and contract/SCHEDULE.md. Zero runtime dependencies. Inside the repo nothing goes through dist/: fero imports ../../data/api/index.ts by relative path and Node runs the .ts under --experimental-strip-types.

The contract

Everything runs under an executable timing contract — contract/SCHEDULE.md (SCHEDULE_VERSION 4): batch commit semantics, read-your-writes, effect isolation, origin-token echo suppression, snapshot-then-deltas subscriptions, emission legality, the deep-path law, and the value-domain portability table, each pinned by conformance/schedule.test.ts.

The delta protocol is deliberately CLOSED (contract/delta.ts): three row verbs (add/update/ remove, update first-class with prev and a path), a separate order channel (orderInsert/orderRemove/orderMove), one scalar shape, one consolidated batch envelope. Every operator consumes and emits exactly this.

Consumer

Inside the repo this library is source-served — node --experimental-strip-types reads the .ts directly; dist/ exists only for npm. Its in-repo consumer is fero (github.com/pemrouz/fero; checked out beside this repo as ../fero-v2) — a replicated, partitioned runtime whose substrate imports the one entry api/index.ts by relative path and applies replication records through the hot lane (seam/index.ts lane()), with fero's CI riding this repo's SCHEDULE conformance suite cross-repo.

import { $, batch } from 'data'            // exports["."] → dist/api/index.js (api/index.ts in-repo)

const orders = $({})                        // an object-born (keyed) source
const active = orders.filter(o => o.active) // an incremental view
const avg    = active.avg('value')          // a scalar view

orders.set('o1', { active: true, value: 42 })
orders.get('o1').update({ active: true, value: 43 })
batch(() => { /* many writes, ONE commit */ })

const sub = active.sink({                   // native per-commit batches, by ref
  init: (snapshot) => {},
  apply: (commit) => {},
})
sub.dispose()

Commands

• npm test — the full suite (unit + the SCHEDULE conformance suite).
• npm run typecheck — four tsc programs, including the shipped types/public.d.ts consumer gate.
• npm run perf — the m1–m4 budget gates (machine-calibrated absolutes).
• npm run build — dist/ for npm (npm run pack:check builds and lists the tarball; prepublishOnly = build + test + typecheck).

History

v4 is the fourth engine: the v2 proxy library and the v3 kernel rewrite — including the landing site, gallery examples, cross-library benchmarks, and e2e layer — were retired when v4 was promoted to the repo root (2026-08-16; all of it remains at the v3 branch tip). v4 = v3 + fero's W1–W17 wishlist (STATUS.md is the ledger) + the adversarial re-evaluation hardening that preceded the promotion.