quick-lru 
Simple “Least Recently Used” (LRU) cache
Useful when you need to cache something and limit memory usage.
Inspired by the hashlru algorithm, but instead uses Map to support keys of any type, not just strings, and values can be undefined.
Install
$ npm install quick-lru
Usage
const QuickLRU = require('quick-lru');
const lru = new QuickLRU({maxSize: 1000});
lru.set('????', '????');
lru.has('????');
//=> true
lru.get('????');
//=> '????'
API
new QuickLRU(options?)
Returns a new instance.
options
Type: object
maxSize
Required
Type: number
The maximum number of items before evicting the least recently used items.
maxAge
Type: number
Default: Infinity
The maximum number of milliseconds an item should remain in cache.
By default maxAge will be Infinity, which means that items will never expire.
Lazy expiration happens upon the next write or read call.
Individual expiration of an item can be specified by the set(key, value, options) method.
onEviction
Optional
Type: (key, value) => void
Called right before an item is evicted from the cache.
Useful for side effects or for items like object URLs that need explicit cleanup (revokeObjectURL).
Instance
The instance is iterable so you can use it directly in a for…of loop.
Both key and value can be of any type.
.set(key, value, options?)
Set an item. Returns the instance.
Individual expiration of an item can be specified with the maxAge option. If not specified, the global maxAge value will be used in case it is specified on the constructor, otherwise the item will never expire.
.get(key)
Get an item.
.has(key)
Check if an item exists.
.peek(key)
Get an item without marking it as recently used.
.delete(key)
Delete an item.
Returns true if the item is removed or false if the item doesn't exist.
.clear()
Delete all items.
.resize(maxSize)
Update the maxSize, discarding items as necessary. Insertion order is mostly preserved, though this is not a strong guarantee.
Useful for on-the-fly tuning of cache sizes in live systems.
.keys()
Iterable for all the keys.
.values()
Iterable for all the values.
.entriesAscending()
Iterable for all entries, starting with the oldest (ascending in recency).
.entriesDescending()
Iterable for all entries, starting with the newest (descending in recency).
.size
The stored item count.
