WeakMap Cache

weak-cache.js

const { log } = console;
const TTL_MN = 5 // mintes
const TTL_MS = TTL_MN * 60 * 1_000 // milliseconds
const MapRefs = new Map();
const Maps = new WeakMap();

function fetchStuff(someId) {
    const ref = MapRefs.get(someId);
    const map = Maps.get(ref);
    const expired = Date.now() - (map?.ts ?? 0) > TTL_MS

    if (!map || expired) {
        const data = { name: "foo_" + someId }; // fake api call
        MapRefs.set(someId, Symbol(someId));
        Maps.set(MapRefs.get(someId), { data, ts: Date.now() });
        return { ...data, DEBUG: "FETCH" };
    }

    return { ...map.data, DEBUG: "CACHE" };
}

log('one one', fetchStuff(11)); // one one { name: 'foo_11', DEBUG: 'FETCH' }
log('one one', fetchStuff(11)); // one one { name: 'foo_11', DEBUG: 'CACHE' }
log('...')                      // ...
log('two two', fetchStuff(22)); // two two { name: 'foo_22', DEBUG: 'FETCH' }
log('two two', fetchStuff(22)); // two two { name: 'foo_22', DEBUG: 'CACHE' }
log('two two', fetchStuff(22)); // two two { name: 'foo_22', DEBUG: 'CACHE' }