@rimbu/hashed

Fast, immutable hash-based maps and sets for TypeScript & JavaScript.

@rimbu/hashed provides efficient, type-safe HashMap and HashSet implementations. These use configurable Hasher instances and Eq equality comparers under the hood, giving you predictable hashing and fast lookups for arbitrary keys and values – from primitives to complex objects and streams.

Use it whenever you need hash-based collections, custom hashing/equality, or want to build rich immutable models backed by persistent data structures.

Table of Contents

1. Why @rimbu/hashed?
2. Feature Highlights
3. Quick Start
4. Core Concepts & Types
5. Configuring Hashers & Contexts
6. Installation
7. Ecosystem & Integration
8. Contributing
9. License
10. Attributions

Why @rimbu/hashed?

Plain JavaScript Map / Set give you basic hash semantics, but you often need:

• Stable hashing for complex values – objects, arrays, tuples, dates, streams.
• Custom equality – case-insensitive strings, domain-specific identity, etc.
• Immutable semantics – structural sharing, safe reuse across your app.

@rimbu/hashed focuses on:

• Configurable hashing via Hasher utilities – choose how values are hashed.
• Pluggable equality via Eq – control when values are considered equal.
• Immutable collections – operations return new HashMap / HashSet instances.
• Context-based factories – HashMap.Context and HashSet.Context let you tune performance characteristics (block size, collision strategy).

If you outgrow the default Map / Set, or need consistent hashing across environments, @rimbu/hashed is a solid fit.

Feature Highlights

• HashMap & HashSet – immutable, type-invariant collections with O(1)-style lookups.
• Non-empty variants – HashMap.NonEmpty / HashSet.NonEmpty for stronger type guarantees.
• Builders – HashMap.Builder / HashSet.Builder for efficient bulk construction and mutation before freezing.
• Configurable contexts – use HashMap.createContext / HashSet.createContext to plug in custom Hasher, Eq, and block sizing.
• Rich hasher utilities – Hasher.numberHasher, Hasher.stringHasher, Hasher.anyDeepHasher, Hasher.objectHasher, and more in @rimbu/hashed/common.
• Stream integration – many APIs accept StreamSource inputs and expose Stream outputs for composable data flows.

Quick Start

import { HashMap, HashSet } from '@rimbu/hashed';

// HashSet: unique values
const users = HashSet.of('alice', 'bob', 'alice');
console.log(users.toString()); // HashSet('alice', 'bob')

// HashMap: key → value entries
const scores = HashMap.of([1, 'low'], [2, 'medium'], [3, 'high']);

console.log(scores.get(2)); // 'medium'
console.log(scores.hasKey(4)); // false

// Immutable updates
const updated = scores.set(2, 'mid');
console.log(updated.get(2)); // 'mid'
console.log(scores.get(2)); // 'medium' (original unchanged)

Try Rimbu (including @rimbu/hashed) live in the browser using the Rimbu Sandbox on CodeSandbox.

Core Concepts & Types

Exported Types (main package)

From @rimbu/hashed:

The package also re-exports the sub-packages:

• @rimbu/hashed/map – HashMap-specific interfaces and helpers.
• @rimbu/hashed/set – HashSet-specific interfaces and helpers.
• @rimbu/hashed/common – shared hasher utilities and low-level building blocks.

Basic Operations (HashMap)

import { HashMap } from '@rimbu/hashed';

// Construction
const empty = HashMap.empty<number, string>();
const fromEntries = HashMap.of([1, 'one'], [2, 'two']);

// Size & emptiness
empty.isEmpty; // true
fromEntries.size; // 2

// Lookups
fromEntries.hasKey(1); // true
fromEntries.get(2); // 'two'

// Removing keys (returns new map)
const without = fromEntries.removeKey(1);
without.hasKey(1); // false

Basic Operations (HashSet)

import { HashSet } from '@rimbu/hashed';

const s1 = HashSet.of('a', 'b', 'c', 'a');

s1.size; // 3
s1.has('b'); // true

const s2 = s1.add('d'); // new set
const s3 = s2.remove('a'); // new set

console.log(s1.toString()); // HashSet('a', 'b', 'c')
console.log(s3.toString()); // HashSet('b', 'c', 'd')

See the Map docs, Set docs, and the Hashed API reference for the complete API surface.

Configuring Hashers & Contexts

One of the strengths of @rimbu/hashed is full control over how values are hashed.

Using Built-in Hashers

import { Hasher } from '@rimbu/hashed/common';

const numHasher = Hasher.numberHasher();
const strHasher = Hasher.stringHasher();
const deepHasher = Hasher.anyDeepHasher();

numHasher.hash(42); // 32‑bit hash
strHasher.hash('Hello');
deepHasher.hash({ a: [1, 2, 3], b: { c: 5 } });

There are many helpers for common scenarios:

• Hasher.numberHasher() / Hasher.booleanHasher() / Hasher.bigintHasher()
• Hasher.stringHasher() / Hasher.stringCaseInsensitiveHasher()
• Hasher.arrayHasher() / Hasher.streamSourceHasher()
• Hasher.objectHasher() / Hasher.objectShallowHasher() / Hasher.objectDeepHasher()
• Hasher.anyFlatHasher() / Hasher.anyShallowHasher() / Hasher.anyDeepHasher()

Custom Contexts for HashMap

import { HashMap } from '@rimbu/hashed';
import { Hasher } from '@rimbu/hashed/common';

// Case-insensitive string keys
const ctx = HashMap.createContext<string>({
  hasher: Hasher.stringCaseInsensitiveHasher(),
});

const m = ctx.of(['Key', 1], ['OTHER', 2]);

m.hasKey('key'); // true
m.hasKey('other'); // true

Custom Contexts for HashSet

import { HashSet } from '@rimbu/hashed';
import { Hasher } from '@rimbu/hashed/common';

// Deep structural hashing for objects
const ctx = HashSet.createContext<{ id: number; tags: string[] }>({
  hasher: Hasher.anyDeepHasher(),
});

const set = ctx.of({ id: 1, tags: ['a', 'b'] }, { id: 2, tags: ['c'] });

set.has({ id: 1, tags: ['a', 'b'] }); // true (structurally equal)

For more on contexts, see the HashMap.Context and HashSet.Context sections in the API reference.

Installation

Node / Bun / npm / Yarn

npm install @rimbu/hashed
# or
yarn add @rimbu/hashed
# or
bun add @rimbu/hashed
# or
deno add npm:@rimbu/hashed

Then:

import { HashMap, HashSet } from '@rimbu/hashed/mod.ts';

Browser / ESM

@rimbu/hashed ships both ESM and CJS builds. Use it with any modern bundler (Vite, Webpack, esbuild, Bun, etc.) or directly in Node ESM projects.

Ecosystem & Integration

• Part of the broader Rimbu collection ecosystem – interoperates with @rimbu/bimap, @rimbu/ordered, @rimbu/collection-types, and @rimbu/stream.
• Ideal for modelling key/value stores, index structures, membership sets, caches, and more.
• Works seamlessly with other Rimbu collections and utilities for building rich, immutable data models.

Explore more at the Rimbu documentation and the Hashed API docs.

Contributing

We welcome contributions! See the Contributing guide for details.

Made with contributors-img.

License

MIT © Rimbu contributors. See LICENSE for details.

Attributions

Created and maintained by Arvid Nicolaas. Logo © Rimbu.