at-decorators

🔧 Fast, dependency-free memoization for TypeScript, built on TC39 Stage 3 decorators — for class methods, getters, and plain functions.

Features

• One API for everything — apply the same memoize to class methods, getters (as a decorator), and standalone functions (as a wrapper).
• Structure-aware cache keys — arguments are serialized (including Map, Set, Date, RegExp, URL, Error, bigint, and circular references) and hashed with SHA3-512, so structurally equal arguments hit the same cache entry.
• Expiration and size limits — per-entry TTL via cacheDuration and a FIFO size cap via maxCacheSizePerTarget.
• Explicit invalidation — group memoized targets into clearable cache groups; caches are tracked via WeakRef, so they never leak.
• Pluggable persistence — back the in-memory cache with any storage (file, Redis, database) through three small callbacks.
• Zero runtime dependencies — ships ESM and CJS with type definitions.

Installation

npm install at-decorators # or yarn add / pnpm add / bun add

Quick Start

import { memoize } from 'at-decorators';

class UserService {
  @memoize
  fetchUser(userId: string): Promise<User> {
    return fetch(`/api/users/${userId}`).then((res) => res.json());
  }

  @memoize
  get config(): Config {
    return loadConfigFromDisk();
  }
}

// Plain functions work too — no decorator syntax required.
const fibonacci = memoize((n: number): number => (n <= 1 ? n : fibonacci(n - 1) + fibonacci(n - 2)));

Repeated calls with structurally equal arguments return the cached result without invoking the original implementation.

Usage

Custom cache settings: memoizeFactory

Create a memoize with your own TTL, size limit, or cache-key derivation:

import { memoizeFactory } from 'at-decorators';

const memoizeShortly = memoizeFactory({
  cacheDuration: 60 * 1000, // Entries expire after 1 minute (default: no expiration).
  maxCacheSizePerTarget: 100, // Keep at most 100 entries per method/getter/function (default: 10,000). The oldest entry is evicted first.
});

class ExchangeRateService {
  @memoizeShortly
  getRate(from: string, to: string): Promise<number> {
    return fetchRate(from, to);
  }
}

Option	Default	Description
cacheDuration	Number.POSITIVE_INFINITY	Milliseconds a cached value stays valid.
maxCacheSizePerTarget	10_000	Maximum entries per memoized target; the oldest entry is evicted when exceeded.
getCacheKey	getCacheKeyOfHash	Derives a string cache key from this and the arguments.
caches	undefined	A registry that receives every created cache, for external tracking/clearing.

Caching only the latest result: memoizeOne

memoizeOne remembers a single entry — ideal when arguments rarely change between consecutive calls and you want O(1) memory:

import { memoizeOne, memoizeOneWithEmptyHash, memoizeOneFactory } from 'at-decorators';

// Re-computes only when the arguments (or `this`) change.
const formatReport = memoizeOne((rows: Row[]) => rows.map(renderRow).join('\n'));

// Ignores arguments entirely — computes once, then always returns the first result.
const loadSettings = memoizeOneWithEmptyHash(() => JSON.parse(fs.readFileSync('settings.json', 'utf8')));

// With a TTL: at most one re-computation per 5 seconds for the same arguments.
const memoizeOneBriefly = memoizeOneFactory({ cacheDuration: 5000 });

Clearable cache groups: createMemoizeCacheGroup

Use createMemoizeCacheGroup when a feature needs both a memoized function/decorator and an explicit invalidation hook:

import { createMemoizeCacheGroup } from 'at-decorators';

const usersCache = createMemoizeCacheGroup({
  cacheDuration: 24 * 60 * 60 * 1000,
  maxCacheSizePerTarget: 10_000,
});

export const memoizeForUsers = usersCache.memoize;
export const clearCachesForUsers = usersCache.clear;

Every target memoized with memoizeForUsers registers its cache in the group, and clearCachesForUsers() empties them all at once. Caches are held via WeakRef, so a group never prevents garbage collection of memoized targets.

Use getGlobalMemoizeCacheStore when several bundles or module instances (e.g. separately bundled route handlers) must share and clear the same cache groups:

import { createMemoizeCacheGroup, getGlobalMemoizeCacheStore } from 'at-decorators';

const cacheStore = getGlobalMemoizeCacheStore(Symbol.for('myAppMemoizeCacheStore'), ['headers', 'users'] as const);

const headersCache = createMemoizeCacheGroup({
  cacheDuration: 10 * 60 * 1000,
  caches: cacheStore.headers,
  maxCacheSizePerTarget: 1000,
});

export const memoizeForHeaders = headersCache.memoize;
export const clearCachesForHeaders = headersCache.clear;

The store lives on globalThis under the given key, so every module instance resolves the same registries. You can also clear an arbitrary collection of caches directly with clearMemoizeCaches(caches).

Persistent caches: memoizeWithPersistentCacheFactory

Keep cached values across process restarts by supplying three storage callbacks. Storage failures are swallowed, so a broken backend degrades to in-memory memoization instead of breaking calls:

import { memoizeWithPersistentCacheFactory } from 'at-decorators';

const createPersistentMemoize = memoizeWithPersistentCacheFactory({
  cacheDuration: 60 * 60 * 1000,
  // `persistCache` and `removeCache` may be async; their results are ignored.
  persistCache: (persistentKey, hash, value, currentTime) => db.upsert(persistentKey, hash, value, currentTime),
  removeCache: (persistentKey, hash) => db.remove(persistentKey, hash),
  // `tryReadingCache` MUST be synchronous and return [value, cachedAt] or undefined;
  // a Promise cannot be awaited here and would silently bypass the persistent lookup.
  tryReadingCache: (persistentKey, hash) => syncDb.read(persistentKey, hash),
});

class GeocodingService {
  @createPersistentMemoize('geocode')
  geocode(address: string): Promise<Coordinates> {
    return callGeocodingApi(address);
  }
}

Each memoized target gets a persistentKey namespace. Lookups check the in-memory cache first, then the persistent storage (synchronously — use a synchronous client or an in-process snapshot for reads); promise results are persisted after they resolve.

Cache key functions

The cache key determines what counts as "the same call". Three implementations are provided, and any (self, args) => string works via the getCacheKey option:

import { getCacheKeyOfHash, getCacheKeyOfStringified, getCacheKeyOfEmptyString, memoizeFactory } from 'at-decorators';

// Default: SHA3-512 hash of the serialized `this` and arguments — fixed-length keys.
const memoizeByHash = memoizeFactory({ getCacheKey: getCacheKeyOfHash });

// Serialized `this` and arguments as-is — faster for small arguments, keys grow with input size.
const memoizeByString = memoizeFactory({ getCacheKey: getCacheKeyOfStringified });

// Ignore `this` and arguments — every call shares one cache entry.
const memoizeIgnoringArgs = memoizeFactory({ getCacheKey: getCacheKeyOfEmptyString });

// Custom: key on a single argument property.
const memoizeByUserId = memoizeFactory({ getCacheKey: (_self, args) => (args[0] as { id: string }).id });

Serialization is powered by an embedded fork of oson, which — unlike JSON.stringify — handles undefined, bigint, NaN, Infinity, Map, Set, Date, RegExp, URL, Error, and circular references (Uint8Array is currently supported only when its contents decode to Latin-1 text). The serializer (stringify) and hash (sha3_512) are exported for direct use.

API Summary

Export	Kind	Description
memoize	decorator	Memoize with default settings (10,000 entries per target, no TTL).
memoizeFactory(options)	factory	Build a memoize with custom TTL, size limit, key function, caches.
memoizeOne / memoizeOneWithEmptyHash	decorator	Cache only the latest result (keyed by arguments / shared).
memoizeOneFactory(options)	factory	Build a memoizeOne with custom TTL or key function.
createMemoizeCacheGroup(options)	factory	A memoize plus a clear() hook over all its caches.
getGlobalMemoizeCacheStore(key, names)	function	Shared, globalThis-backed cache registries for cross-bundle groups.
clearMemoizeCaches(caches)	function	Clear every cache in an iterable of caches.
memoizeWithPersistentCacheFactory(options)	factory	Memoization backed by user-provided persistent storage.
getCacheKeyOfHash / getCacheKeyOfStringified / getCacheKeyOfEmptyString	function	Built-in cache-key derivations.
stringify(value)	function	Structure-preserving serialization (oson format).
sha3_512(text)	function	SHA3-512 hex digest of a string.

Requirements

• Decorators: TypeScript 5.0+ (standard decorators, i.e. without experimentalDecorators), or Babel with @babel/plugin-proposal-decorators (version: '2023-11').
• Runtime: Node.js 24+ (per the engines field); plain-function usage requires no decorator support at all.

Contributing

Issues and pull requests are welcome. Run yarn install, make your changes, and verify with yarn test and yarn verify.

License

Apache-2.0 © WillBooster Inc. — see LICENSE and NOTICE. Includes code derived from oson (MIT) and js-sha3 (MIT).