WeakIdentityMap

The WeakIdentityMap object holds key-value pairs of weakly referenced objects and remembers the original insertion order of the keys.

A weak reference to an object is a reference that does not prevent the object from being reclaimed by the garbage collector. In contrast, a normal (or strong) reference keeps an object in memory.

Identity Map ensures that each object gets loaded only once by keeping every loaded object in a map. Looks up objects using the map when referring to them.

– Martin Fowler

WeakIdentityMap is based on Map, WeakRef and FinalizationRegistry objects.

• No dependencies
• TypeScript
• ES2021
• Node.js >=14.6.0

Installation

npm i weak-identity-map

Example

const map = new WeakIdentityMap();

let entity = {};

map.set('key', entity);

// returns a reference to the entity
map.get('key');

entity = null;

// ...
// GC reclaims space
// ...

// returns undefined
map.get('key');

API

size: number

Returns the number of values in the WeakIdentityMap object.

set(any, object): this

The set() method adds or updates an element with a specified key and an object to a WeakIdentityMap object.

get(any): object | undefined

The get() method returns a reference to a specified object from a WeakIdentityMap object.

has(any): boolean

The has() method returns a boolean indicating whether an object with the specified key exists or not.

delete(any): boolean

The delete() method removes the specified object from a WeakIdentityMap object by key.

keys(): IterableIterator<any>

The keys() method returns a new Iterator object that contains the keys for each element in the WeakIdentityMap object in insertion order.

entries(): IterableIterator<[any, object]>

The entries() method returns a new Iterator object that contains the [key, value] pairs for each element in the WeakIdentityMap object in insertion order.

values(): IterableIterator<object>

The values() method returns a new Iterator object that contains the values for each element in the WeakIdentityMap object in insertion order.

forEach(cb): void

The forEach() method executes a provided function once per each key/value pair in the WeakIdentityMap object, in insertion order.

clear(): void

The clear() method removes all elements from a WeakIdentityMap object.

License

WeakIdentityMap is MIT licensed.