http-cache.service.ts

const maxAge = 30; // maximum cache age (min)

/**
   * Gets the cached data for the specified request.
   * @param url The request URL.
   * @return The cached data or null if no cached data exists for this request.
   */
  getCacheData(url: string): HttpResponse<any> | null {
    const cacheEntry = this.cachedData[url];

    if (cacheEntry) {
      const exiprationDate = new Date();
      exiprationDate.setMinutes(exiprationDate.getMinutes() - maxAge);
      if (new Date(exiprationDate).getTime() >= new Date(cacheEntry.lastUpdated).getTime()) {
        return null;
      } else {
        return cacheEntry.data;
      }
    }

    return null;
  }