LFUCache.js

/**
 * @param {number} capacity
 */
var LFUCache = function(capacity) {
    this.capacity = capacity;
    this.storage = {};
};

/** 
 * @param {number} key
 * @return {number}
 */
LFUCache.prototype.get = function(key) {
    if(this.storage[key]) {
        this.storage[key][1] += 1;
        this.storage[key][2] = new Date();
        return this.storage[key][0];   
    } else {
        return -1;
    }
};

/** 
 * @param {number} key 
 * @param {number} value
 * @return {void}
 */
LFUCache.prototype.put = function(key, value) {
    if (Object.keys(this.storage).length === this.capacity) {
        let minFreq = Infinity;
        let minKeys = [];
        
        for(let i = 0; i < Object.keys(this.storage).length; i++) {
            if (this.storage[Object.keys(this.storage)[i][1]] < minFreq){
                minKeys = [Object.keys(this.storage)[i]];
            } else if (this.storage[Object.keys(this.storage)[i][1]] === minFreq) {
                minKeys.push(Object.keys(this.storage)[i])
            }
        }
        
        let leastRecentDate = new Date();
        let leastRecentKey;
        
        for(let j = 0; j < minKeys.length; j++) {
            if(minKeys[j][2] < leastRecentDate) {
                leastRecentDate = minKeys[j][2];
                leastRecentKey = minKeys[j];
            }
        }
        
        delete this.storage[leastRecentKey];
    }
    
    this.storage[key] = [value, 0, new Date()]
};

/** 
 * Your LFUCache object will be instantiated and called as such:
 * var obj = Object.create(LFUCache).createNew(capacity)
 * var param_1 = obj.get(key)
 * obj.put(key,value)
 */