cache

Zero-dependency in-memory key-value cache with pluggable eviction policies, capacity limits, and optional TTL.

cache is a zero-dependency in-memory key-value cache with pluggable eviction policies, capacity limits, and optional TTL.

Motivation

A hand-rolled Map-based cache without a capacity limit is a memory leak waiting to happen — nothing ever gets removed. Reaching for a library instead usually means choosing between something that bakes in one eviction algorithm (LRU only, no LFU or FIFO) or a full-featured cache far bigger than a lean cache needs (cost-based sizing, stale-while-revalidate).

cache keeps the core cache policy-agnostic: createCache(capacity, options?) handles storage, capacity, and TTL, while the eviction algorithm is a small object you pass in. Five are built in — lru(), lfu(), mru(), mfu(), and fifo() — and the EvictionPolicy interface is public, so you can write your own without forking the package.

Features

• Eviction policies: lru() (default), lfu(), mru(), mfu(), and fifo(), swappable via createCache(capacity, { policy }).
• Capacity and eviction: a count-based capacity evicts one entry — chosen by the configured policy — right before an insert that would exceed it.
• TTL: optional and lazy, checked on get/has/peek, no background sweep timer. A cache-wide default and a per-entry override.
• onEvict: fires on capacity or TTL eviction — not on manual delete() or clear().
• peek: reads a value without affecting eviction order.
• Custom policies: EvictionPolicy<K> is a public interface — implement your own algorithm (random replacement, …) as a plain object, no subclassing.
• Iteration: keys(), values(), entries(), and [Symbol.iterator]() walk live entries in insertion order.
• Tree-shakeable — every policy has its own subpath export (@zap-studio/cache/lru, /lfu, /mru, /mfu, /fifo); unused policies are dropped by any modern bundler.

Quick Start

import { createCache } from "@zap-studio/cache";

const cache = createCache<string, number>(100); // lru() by default

cache.set("a", 1);
cache.get("a"); // 1
cache.has("a"); // true
cache.size; // 1

Runtime Support

The package ships standard ESM only and uses no runtime-specific APIs. Deno 1.42 is the first release that can install packages from JSR (deno add jsr:@zap-studio/cache).

Learn More

• Getting Started — install and build your first cache step by step
• Eviction Policies — lru(), lfu(), mru(), mfu(), fifo()
• Capacity and Eviction
• TTL
• onEvict
• peek
• Custom Policies
• Iteration