A TimeCache is a subclass of Map where keys become invalidated after a certain amount of time

TimeCache.js

DEFAULT_CACHE_TIME_MS = 262144; // ~5 minutes (closest 1-bin value)

export default class TimeCache extends Map {
    constructor(cacheTime, seed) {
        super(seed);
        this.cacheTime = cacheTime || DEFAULT_CACHE_TIME_MS;
    }

    set(key, value, cacheTime) {
        super.set(key, {
            expires: Date.now() + (cacheTime || this.cacheTime),
            data: value
        });
    }

    get(key) {
        var entry = super.get(key);
        if (entry && Date.now() < entry.expires) {
            return entry.data;
        } else if (entry) {
            super.delete(key);
        }
    }

    has(key) {
        if (super.has(key)) {
            var entry = super.get(key);
            if (entry && Date.now() < entry.expires) {
                return super.has(key);
            } else if (entry) {
                super.delete(key);
            }
        }
        return false;
    }

    static get [Symbol.species]() { return Map; }
}