code: function(update, options) {
            var count = 0
            for (var id in this.cache) {
              count += 1
              if (update.$inc) {
                this.cache[id].count += update.$inc
              } else {
                this.cache[id].count -= update.$dec
              }
            }
            return count
          }
docs: post-updateConfig-memCacheCounterAdvanced pre-update-memCacheCounterAdvanced