Not So Weak

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Iterable WeakMap (WKey) and WeakSet (WSet) through FinalizationRegistry and WeakRef primitives, reimplementing also the WeakValue (WValue) module, including the optional callback for collected values.

// const {WSet, WKey, WValue} = require('not-so-weak');
import {WSet, WKey, WValue} from 'not-so-weak';

// class WSet<T extends object> extends WeakSet implements Set {}
// class WKey<K extends object, V> extends WeakMap implements Map {}
// class WValue<K, V extends object> extends Map {}

// node --expose-gc example
const ws = new WSet([{}]);
const wm = new WKey([[{}, 'value']]);

const wv = new WValue;
wv.set('value', {}, function (key) {
  console.assert(this === wv);
  console.assert(key === 'value');
  console.log(key, 'value collected');
});

console.assert(ws.size === 1);
console.assert(wm.size === 1);
console.assert([...wm.values()][0] === 'value');
console.assert([...wv.keys()][0] === 'value');

setTimeout(() => {
  gc();
  console.assert(ws.size === 0);
  console.assert(wm.size === 0);
  console.assert(wv.size === 0);
});

Suitable For

• Weak key/value based state/store
• Server Side related tasks that can't bother with manual removal of weakly referenced entries
• every case where you end up swapping to Map or Set because you realize you cannot iterate over their Weak counterpart
• every case where you think there's a memory leak due possibly missing weakThing.delete(ref) operations

Not Suitable For

• raw performance or benchmarks against Map or Set
• every case where weakThing.delete(ref) is already handled by the library or framework logic