I have been looking into a caching solution for a node project of mine and I think this library looks very useful!. One thing I think could be a great addition though is to have a maximum cache size (perhaps either number of entries or memory size) which when exceeded will cause the check routine to evict the oldest entries from the cache to bring it back down to this size.

This of course would be entirely optional and if not set the cache would operate exactly as it does now.