Isaac's lru-cache 2.5.0 plus: cached items may have individual expirations.

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lru cache plus
A cache object that deletes the least-recently-used items.


var LRU = require("lru-cache")
  , options = { max: 500
              , length: function (n) { return n * 2 }
              , dispose: function (key, n) { n.close() }
              , maxAge: 1000 * 60 * 60 }
  , cache = LRU(options)
  , otherCache = LRU(50) // sets just the max size

cache.set("key", "value")
cache.get("key") // "value"

cache.reset()    // empty the cache

If you put more stuff in it, then items will fall out.
If you try to put an oversized thing in it, then it'll fall out right away.


  • max The maximum size of the cache, checked by applying the length
function to all values in the cache. Not setting this is kind of silly, since that's the whole purpose of this lib, but it defaults to Infinity.
  • maxAge Maximum age in ms. Items are not pro-actively pruned out
as they age, but if you try to get an item that is too old, it'll drop it and return undefined instead of giving it to you.
  • length Function that is used to calculate the length of stored
items. If you're storing strings or buffers, then you probably want to do something like function(n){return n.length}. The default is function(n){return 1}, which is fine if you want to store n like-sized things.
  • dispose Function that is called on items when they are dropped
from the cache. This can be handy if you want to close file descriptors or do other cleanup tasks when items are no longer accessible. Called with key, value. It's called before actually removing the item from the internal cache, so if you want to immediately put it back in, you'll have to do that in a nextTick or setTimeout callback or it won't do anything.
  • stale By default, if you set a maxAge, it'll only actually pull
stale items out of the cache when you get(key). (That is, it's not pre-emptively doing a setTimeout or anything.) If you set stale:true, it'll return the stale value before deleting it. If you don't set this, then it'll return undefined when you try to get a stale entry, as if it had already been deleted.


  • set(key, value, max)
  • get(key) => value
Both of these will update the "recently used"-ness of the key.
They do what you think. `max` is optional and overrides the
cache `max` option if provided.
  • peek(key)
Returns the key value (or `undefined` if not found) without
updating the "recently used"-ness of the key.

(If you find yourself using this a lot, you *might* be using the
wrong sort of data structure, but there are some use cases where
it's handy.)
  • del(key)
Deletes a key out of the cache.
  • reset()
Clear the cache entirely, throwing away all values.
  • has(key)
Check if a key is in the cache, without updating the recent-ness
or deleting it for being stale.
  • forEach(function(value,key,cache), [thisp])
Just like `Array.prototype.forEach`.  Iterates over all the keys
in the cache, in order of recent-ness.  (Ie, more recently used
items are iterated over first.)
  • keys()
Return an array of the keys in the cache.
  • values()
Return an array of the values in the cache.