flru

library1.0.2jsnpmunverified

A tiny (215B) and fast Least Recently Used (LRU) cache for JavaScript. Stable version 1.0.2, last updated in 2019. No active release cadence; essentially stable and minimal. Key differentiators: extremely small size (215B), high performance with a two-cache internal architecture that trades memory for speed, supports ESM, CJS, and UMD formats, and includes TypeScript types. Compared to alternatives like lru-cache or tiny-lru, flru is much smaller and faster for typical operations but uses 2n memory and has a simpler API.

storage

npm install flru

github ↗package ↗homepage ↗

INSTALL

IMPORT

SIG · FLRU

flru

storagejavascriptv1.0.2

harness data pending

Install & Compatibility

Where this runs

No compatibility data collected yet for this library.

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

flru

✓ import flru from 'flru'

✗ import { flru } from 'flru'

Default export only; named import will not work. CJS: const flru = require('flru').

flru

✓ const flru = require('flru')

✗ const { flru } = require('flru')

CJS: flru is the default export, not a named export.

CacheType

✓ import type { CacheType } from 'flru'

If you use TypeScript, you can import the CacheType interface. It is not required.

Creates an LRU cache with max 3 items, demonstrates set, get, has, eviction, and clear.

import flru from 'flru'; const cache = flru(3); // max 3 items cache.set('a', 1); cache.set('b', 2); cache.set('c', 3); cache.has('a'); // true cache.get('a'); // 1 cache.set('d', 4); // evicts oldest (b) cache.get('b'); // undefined cache.clear(); cache.has('a'); // false

Debug

Known issues

gotchaflru uses two internal caches (active and stale) and stores up to 2n items. Memory usage is roughly double the limit compared to single-cache LRU implementations.

fix

Consider memory implications when using with large limits.

affects: >=1.0.0

gotchaget() does NOT promote a key to the active cache if the key is in the stale cache; it returns the value but the key may be evicted later.

fix

Read the documentation on the two-cache architecture to understand eviction behavior.

affects: >=1.0.0

gotchaThe default max is 1, which is inefficient and likely not what you want. Always specify a max.

fix

Always pass a positive integer to flru().

affects: >=1.0.0

deprecatedThe package appears unmaintained since 2019. No known security issues, but consider alternatives for long-term support.

fix

Evaluate lru-cache or tiny-lru for active maintenance.

affects: 1.0.2

Errors

Common errors & fixes

import { flru } from 'flru'

Trying to import flru as a named export instead of default.

fix

Use import flru from 'flru'

const { flru } = require('flru')

CJS destructuring on a default export.

fix

Use const flru = require('flru')

flru is not a function

Using flru without calling it, e.g., assigning flru instead of flru(3).

fix

Call flru with a max number: const cache = flru(3)

Upgrade

Version history

1.0.2latest on npm

Audit

Dependencies

No dependency data recorded yet.

Agent activity

24 hits · last 30 days

node

Amazon

Resources

githubhttps://github.com/lukeed/flru ↗

packageflru ↗

homepagehttps://github.com/lukeed/flru#readme ↗