code: function compare (a, b) {
      if (a.timeStamp > b.timeStamp) {
        return -1;
      }
      if (a.timeStamp < b.timeStamp) {
        return 1;
      }
  
      return 0;
    }
docs: Cache size has been exceeded, create list of images sorted by timeStamp So we can purge the least recently used image