@m4x1m1l14n/cache

Lightweight in-memory isomorphic cache implementation with TTL for browser & Node JS

This simple cache is written in TypeScript and works both for browser and Node. It is build on top of built-in Map thus theoretical limit for stored entries is in case of Node 2 ^ 24, which is approximately 16.6 million. Each entry in cache can has its own TTL (timeout) and assigned expiration callback fired once entry expire.

Table of Contents

• Installation
• Documentation
  • Instantiation
  • set
  • get
  • take
  • has
  • delete
  • flush

Installation

npm i @m4x1m1l14n/cache

Documentation

Instantiation

Cache implementation uses templates so when you use this library in TypeScript project, you can restrict what type of key and value cache has to consume.

import { Cache } from '@m4x1m1l14n/cache';

const cache = new Cache<number, string>();

Cache behavior can be altered with options object passed to its constructor. Following table shows options that can be changed.

| Option | Default value | Description | | ---------- | ------------- | ------------------------------------------------------------------- | | resolution | 1000 | Interval in milliseconds after which entries are checked for expiry | | defaultTTL | Infinity | Default TTL for all added entries | | maxItems | 1000 | Maximum number of entries stored in cache |

Example:

import { Cache, CacheOptions } from '@m4x1m1l14n/cache';

const options: CacheOptions = {
	resolution: 1000,
	defaultTTL: Number.POSITIVE_INFINITY,
	maxItems: 1000,
};

const cache = new Cache<number, string>(options);

set

Store value in cache under specified key.

Prototype:

public set( key : K, value : T, ttl? : number, callback?: ExpirationCallback<T> ) : Cache<K, T>;

Params:

• key: Key under which value will be stored
• value: Value to store
• ttl (optional): Timeout after which cache entry will expire and will be deleted
• callback (optional): Callback invoked once entry expire

Return value:

set method returns itself, so it is possible to chain multiple sets

import { Cache } from '@m4x1m1l14n/cache';

const cache = new Cache<number, string>();

cache.set(1, 'Hello').set(2, 'World').set(3, '!');

Example:

import { Cache } from '@m4x1m1l14n/cache';

const cache = new Cache<number, string>();

// Key 1 will persist in cache until standardTTL is reached
cache.set(1, 'Hello');
// Key 2 will expire after 5 seconds
cache.set(2, 'World', 5000);
// Key 3 will expire after 3 seconds, and callback is called
cache.set(3, 'Some other value', 3000, (value) => {
	console.log(`'${value}' has expired`);
	// Expected output
	// > 'Some other value' has expired
});

get

Retrieve value of cached entry by its key.

Prototype:

public get( key : K, refresh = false ) : T | undefined

Params:

• key: Key to retrieve
• refresh (default: false): Whether to refresh entry TTL or not. In case true is passed, item TTL is refreshed and its expiration is postponed, like item is freshly inserted in cache.

Return value:

get returns value assigned to specified key. If key is not found in cache, undefined is returned.

Example:

import { Cache } from '@m4x1m1l14n/cache';

const cache = new Cache<number, string>();

cache.set(1, 'Hello');
console.log(cache.get(1));
// Expected output
// > Hello

take

Retrieve value of cached entry by its key and remove it from cache.

Prototype:

public take( key: K ): T | undefined

Params:

• key: Key to retrieve

Return value:

take returns value assigned to specified key. If key is not found in cache, undefined is returned.

Example:

import { Cache } from '@m4x1m1l14n/cache';

const cache = new Cache<number, string>();

cache.set(1, 'Hello');
console.log(cache.take(1));
console.log(cache.take(1));
// Expected output
// > Hello
// > undefined

has

Returns wether cache contains specified key or not.

Prototype:

public has( key : K ) : boolean

Params:

• key: Key to check for

Return value:

true in case key exists in cache, false otherwise

Example:

import { Cache } from '@m4x1m1l14n/cache';

const cache = new Cache<number, string>();

cache.set(1, 'Hello');
console.log(cache.has(1));
console.log(cache.has(2));
// Expected output
// > true
// > false

delete

Removes cache entry by specified key.

Prototype:

public delete( key : K ) : boolean

Params:

• key: Key of entry to remove

Return value:

true in case key was removed, false otherwise

Example:

import { Cache } from '@m4x1m1l14n/cache';

const cache = new Cache<number, string>();

cache.set(1, 'Hello');
console.log(cache.get(1));
console.log(cache.delete(1));
console.log(cache.get(1));
console.log(cache.delete(1));
// Expected output
// > Hello
// > true
// > undefined
// > false

flush

Clears all entries from the cache, with an option to invoke expiration callbacks for each entry before deletion.

Prototype:

public flush(invokeCallback: boolean = false) : void

Params:

• invokeCallback (default: false): If set to true, any expiration callback assigned to an entry will be called before the entry is deleted.

Return value:

flush does not return a value.

Example:

import { Cache } from '@m4x1m1l14n/cache';

const cache = new Cache<number, string>();

cache.set(1, 'Hello', 1000, (value) => {
	console.log(`'${value}' has expired`);
});
cache.set(2, 'World', 2000, (value) => {
	console.log(`'${value}' has expired`);
});

// Flush cache and invoke callbacks
cache.flush(true);
// Expected output:
// > 'Hello' has expired
// > 'World' has expired

// Flush cache without invoking callbacks
cache.flush();