This module implements a simple, fixed-size*, least-recently-used (LRU) cache.
*Note that this is a fixed number of items, not a fixed amount of memory, so it really only makes sense to use with relatively homogenous objects.
This module was developed as part of a programming exercise, and hasn't been tested in production, so use with appropriate caution.
git clone https://github.com/femto113/node-lru-cache
cd node-lru-cache
npm linkThis module exports an object constructor for an LRU object, which takes the maximum number of items to hold in the cache as an argument.
var LRU = require("lru-cache");
var lru = new LRU(3);The LRU object offers just a few methods:
put(key, value)
Add an new item to the cache, or replace an existing item's value. If the cache is full it will eject the oldest item.
get(key)
Retrieve an item from the cache. If not found (either because it wasn't added or because it was ejected) will return null. If found will update the timestamp of the item.
oldest()
Retrieve the oldest item in the cache (without updating its timestamp). Useful to see what's about to be ejected.
full
Boolean property indicating whether the cache is full.
This cache uses two complementary datastructures to provide fast performance of each operation. A standard Javascript object is used as a hash table for O(1) lookup by key, and a min-heap (provided by the heap module is used to maintain the LRU sort. The get and put operations are both O(log N) in theory but due to the magical performance properties of heaps will be close to O(1) in practice.
MIT