lru

library3.1.0jsnpmunverified

A minimal O(1) LRU cache for Node.js supporting set, get, peek, remove, clear, and eviction events. Version 3.1.0 is stable and suitable for small caches. It uses a linked list and hash map for O(1) operations. Differentiators: simple API, evict event, optional maxAge for TTL, and CommonJS support. No TypeScript types, no ESM. Suitable for Node >= 0.4.0.

storage

npm install lru

github ↗package ↗homepage ↗

INSTALL

IMPORT

SIG · LRU

lru

storagejavascriptv3.1.0

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.

LRU

✓ const LRU = require('lru');

✗ import LRU from 'lru';

Package is CommonJS only; ESM import will fail.

LRU (with options)

✓ const cache = new LRU({ max: 100, maxAge: 60000 });

✗ const cache = new LRU(100, 60000);

Options must be passed as an object, not separate arguments.

evict event

✓ cache.on('evict', function(data) { console.log(data.key, data.value); });

✗ cache.on('evict', (data) => { console.log(data.key); });

Arrow functions are fine, but ensure 'this' context is not needed.

Creates an LRU cache with max 2 items, listens for evict event, and demonstrates set/get/remove/clear.

const LRU = require('lru'); const cache = new LRU(2); let evicted; cache.on('evict', function(data) { evicted = data; }); cache.set('foo', 'bar'); cache.get('foo'); // => 'bar' cache.set('foo2', 'bar2'); cache.set('foo3', 'bar3'); // evicted => { key: 'foo', value: 'bar' } console.log(cache.length); // 1 console.log(cache.keys); // ['foo3'] cache.remove('foo2'); // => 'bar2' cache.clear(); console.log(cache.length); // 0

Debug

Known issues

gotchaThe `length` property is not a function; it's a number.

fix

Access `cache.length` directly, not `cache.length()`.

affects: >=1.0.0

gotcha`cache.remove()` returns the value if key exists, else undefined.

fix

Check return value for existence: const val = cache.remove(key); if (val !== undefined) { ... }

affects: >=1.0.0

gotcha`cache.clear()` does NOT emit the 'evict' event.

fix

Manually emit evict events before clear if needed.

affects: >=1.0.0

gotchaThe `maxAge` option is in milliseconds, not seconds.

fix

Set `maxAge` in milliseconds.

affects: >=2.0.0

gotchaThe `get` method will return `undefined` for expired items (if maxAge set) without emitting evict.

fix

Use `peek` if you want to check without marking as recently used.

affects: >=2.0.0

deprecatedThe package has no TypeScript type definitions.

fix

Create own `.d.ts` or use `@types/lru` if available.

affects: >=1.0.0

gotchaConstructor accepts either a number (max items) or an options object.

fix

Pass options object with `max` and optionally `maxAge`.

affects: >=2.0.0

Errors

Common errors & fixes

TypeError: lru is not a function

Importing the package incorrectly (ESM import instead of require).

fix

Use `const LRU = require('lru');`

TypeError: cache.length is not a function

Calling `cache.length()` as a function, but it's a property.

fix

Use `cache.length` without parentheses.

ReferenceError: LRU is not defined

Capitalization error or missing require.

fix

Ensure `const LRU = require('lru');` is present.

TypeError: cache.on is not a function

Calling `on` before cache is initialized, or using a plain object.

fix

Create a new LRU instance first: `const cache = new LRU(10);`

Upgrade

Version history

3.1.0latest on npm

Audit

Dependencies

No dependency data recorded yet.

Agent activity

18 hits · last 30 days

node

Resources

githubssh://git@github.com/chriso/lru ↗

packagelru ↗

homepagehttp://github.com/chriso/lru ↗