index.js

'use strict';
let cache = {};

const isDefined = (item) => {
        return typeof item !== 'undefined';
    }

    , isExpired = (key) => {
        const currentTime = new Date();

        let expired;

        if (cache[key].expires === Infinity){
            expired = false;
        } else {
            expired = !!(currentTime.getTime() >= cache[key].expires.getTime() || cache[key].expires === 0);
        }

        if (expired){
            // clear this item from cache
            delete cache[key];
        }

        return expired;
    }

    , getFromCache = (key) => {
        if (isDefined(cache[key]) && !isExpired(key)) {
            cache[key].uses++;

            return cache[key].data;
        } else {
            return null;
        }
    }

    , cacheEntries = () => {
        const obj = {};

        Object.keys(cache).forEach((item) => {
            obj[item] = { expires: cache[item].expires, uses: cache[item].uses };
        });

        return obj;
    }

    , clearCache = (pruneThreshold) => {
        if (isDefined(pruneThreshold)) {
            Object.keys(cache).forEach((item) => {
                if (cache[item].uses <= pruneThreshold && cache[item].expires !== Infinity){
                    delete cache[item];
                }
            });
        } else {
            cache = {};
        }
    }

    , pruneCache = (threshold) => {
        return clearCache(threshold);
    }

    , removeFromCache = (key) => {
        if (!isDefined(key)) {
            throw new Error('key must be passed in');
        }

        if (isDefined(cache[key])) {
            return delete cache[key];
        } else {
            return false;
        }
    }

    , addToCache = (key, object, expiresIn) => {
        const expires = expiresIn || 300000;

        cache[key] = {
            data: object
            , expires: 0
            , uses: 0
        };

        // permenant cache option... pass in Infinity as the expires period
        if (expires === Infinity){
            cache[key].expires = Infinity;
        } else {
            cache[key].expires = new Date(new Date().getTime() + expires);
        }
    };

module.exports = {
    get: getFromCache
    , clear: clearCache
    , remove: removeFromCache
    , entries: cacheEntries
    , add: addToCache
    , prune: pruneCache
};