quick-lru/index.d.ts

Simple “Least Recently Used” (LRU) cache

export type Options<KeyType, ValueType> = {
	/**
	The maximum number of milliseconds an item should remain in the cache.

	@default Infinity

	By default, `maxAge` will be `Infinity`, which means that items will never expire.
	Lazy expiration upon the next write or read call.

	Individual expiration of an item can be specified by the `set(key, value, maxAge)` method.
	*/
	readonly maxAge?: number;

	/**
	The maximum number of items before evicting the least recently used items.
	*/
	readonly maxSize: number;

	/**
	Called right before an item is evicted from the cache.

	Useful for side effects or for items like object URLs that need explicit cleanup (`revokeObjectURL`).
	*/
	onEviction?: (key: KeyType, value: ValueType) => void;
};

// eslint-disable-next-line @typescript-eslint/naming-convention
export default class QuickLRU<KeyType, ValueType> extends Map<KeyType, ValueType> implements Iterable<[KeyType, ValueType]> {
	/**
	Simple ["Least Recently Used" (LRU) cache](https://en.m.wikipedia.org/wiki/Cache_replacement_policies#Least_Recently_Used_.28LRU.29).

	The instance is an [`Iterable`](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Iteration_protocols) of `[key, value]` pairs so you can use it directly in a [`for…of`](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Statements/for...of) loop.

	@example
	```
	import QuickLRU from 'quick-lru';

	const lru = new QuickLRU({maxSize: 1000});

	lru.set('🦄', '🌈');

	lru.has('🦄');
	//=> true

	lru.get('🦄');
	//=> '🌈'
	```
	*/
	constructor(options: Options<KeyType, ValueType>);

	[Symbol.iterator](): IterableIterator<[KeyType, ValueType]>;

	/**
	Set an item. Returns the instance.

	Individual expiration of an item can be specified with the `maxAge` option. If not specified, the global `maxAge` value will be used in case it is specified in the constructor, otherwise the item will never expire.

	@returns The list instance.
	*/
	set(key: KeyType, value: ValueType, options?: {maxAge?: number}): this;

	/**
	Get an item.

	@returns The stored item or `undefined`.
	*/
	get(key: KeyType): ValueType | undefined;

	/**
	Check if an item exists.
	*/
	has(key: KeyType): boolean;

	/**
	Get an item without marking it as recently used.

	@returns The stored item or `undefined`.
	*/
	peek(key: KeyType): ValueType | undefined;

	/**
	Delete an item.

	@returns `true` if the item is removed or `false` if the item doesn't exist.
	*/
	delete(key: KeyType): boolean;

	/**
	Delete all items.
	*/
	clear(): void;

	/**
	Update the `maxSize` in-place, discarding items as necessary. Insertion order is mostly preserved, though this is not a strong guarantee.

	Useful for on-the-fly tuning of cache sizes in live systems.
	*/
	resize(maxSize: number): void;

	/**
	The stored item count.
	*/
	get size(): number;

	/**
	The set max size.
	*/
	get maxSize(): number;

	/**
	Iterable for all the keys.
	*/
	keys(): IterableIterator<KeyType>;

	/**
	Iterable for all the values.
	*/
	values(): IterableIterator<ValueType>;

	/**
	Iterable for all entries, starting with the oldest (ascending in recency).
	*/
	entriesAscending(): IterableIterator<[KeyType, ValueType]>;

	/**
	Iterable for all entries, starting with the newest (descending in recency).
	*/
	entriesDescending(): IterableIterator<[KeyType, ValueType]>;
}