cachetree.js

CacheTree is a class for storing client-side data objects in a nested object structure. Data can be easily retrieved by passing an object as a filter into one of its methods. CacheTree can also give an approximation of data missing using a diff method to reduce the amount of data needed to be fetched. CacheTree also implements a Least Recently Used cache replacement algorithm to limit the amount of memory used by the cache.

Use

Create a new cacheTree with the new operator. The constructor takes two arguments: hierarchy[array], maxSize[number][optional]. The first argument is an array of strings. The order of the array determines the hierarchy of the tree, the first element being the top level, and the last element being at the bottom. A second optional argument is a number (positive integer) that gives the maximum number of objects to be stored in the cache before evicting data.

const cache = new CacheTree(['level_1', 'level_2', ..., 'level_n']);

Tests

There are tests for each method in the API. Please see the tests for descriptions and expected behavior.

LRU algorithm

CacheTree implements a Least Recently Used cache replacement algorithm. As data is added to the cache, a linked list keeps the order of new data and recently accessed data. New and recently used data is placed in the front of the list, while unused cached data works its way towards the end of the list. When the cache reaches it's maxSize, old data is removed from the list and cache.

API

Method	Arguments	Return	Description
get	filter[object]	array	Returns an array of data stored in the cache that satisfies the filter. Each data object is a new object.
set	data[object or array]	none	Inserts a data object or an array of data objects into the cache. The data is nested into the cache object by its keys and hierarchy provided in the constructor.
clone	none	object	Creates a new CacheTree object with the same cache object and linked list.
has	filter[object]	boolean	Returns false if cache is missing any part of the cartesian product of the parameters provided in the filter. Returns true otherwise.
getDiff	paramFilter[object]	object	Returns an object similar to paramFilter. The returned object describes the smallest cartesian product of parameters needed to fill in missing data for paramFilter.
clearCache	none	none	Replaces the cache with an empty object and creates a new linked list.
getSize	none	number	Returns the number of data objects stored in the cache.
extract	filter[object]	array	Like get, but removes returned data from cache.

Environment variables

To log console errors when the cache has missing parameters upon get() or extract() calls, set the process.env.CACHE_TREE_LOG_LEVEL variable in your node environment to 'error'.