A ttl cache for use with Dataloader's cacheMap option

ttl-cache.ts

export const ttlCache = <K extends string, V = any>({ ttl, maxSize }: { ttl: number, maxSize?: number }) => {
  let cache: Record<K, { value: V; expiresAt: number } | undefined> = Object.create(null);

  return {
    set: (key: K, value: V) => {
      const keys = Object.keys(cache) as K[];
      if (maxSize && keys.length === maxSize) {
        delete cache[keys[0]]; 
      }

      cache[key] = { value, expiresAt: Date.now() + ttl })
    },
    get: (key: K) => {
      const entry = cache[key];
      if (!entry) {
        return undefined;
      }

      if (entry.expiresAt < Date.now()) {
        delete cache[key];
        return undefined;
      }

      return entry.value;
    },
    clear: () => (cache = Object.create(null)),
    delete: (key: K) => (cache[key] = undefined),
  };
};

@madiganz feel free to copy/change/redistribute as you please