LFUcache.js

/**
 * @param {number} capacity
 */
var LFUCache = function(capacity) {
  this.capacity = capactiy;
  this.storage = {};
  this.freq = {};
  this.lastVisited = [];
};

/** 
 * @param {number} key
 * @return {number}
 */
LFUCache.prototype.get = function(key) {
  if (!this.storage[key]) {
    return -1;
  } else {
    this.freq[key] += 1;
    this.lastVisited.push(key);
    return this.storage[key];
  }
};

/** 
 * @param {number} key 
 * @param {number} value
 * @return {void}
 */
LFUCache.prototype.put = function(key, value) {
  var lfuKey;

  if (!this.capacity) {
    var leastFreqKeys = [];
    var leastCount = +Infinity;
    for (var key in this.freq) {
      if (this.freq[key] < leastCount) {
        leastCount = this.freq[key];
        leastFreqKeys = [key];
      } else if (this.freq[key] === leastCount) {
        leastFreqKeys.push(key);
      }
    }

    if (leastFreqKeys.length === 1) {
      lfuKey = leastFreqKeys[0];
    } else {
      var leastVisited;
      var leastVisitedIndex = +Infinity;
      for (var i = 0; i < leastFreqKeys.length; i++) {
        if (this.lastVisited.lastIndexOf(leastFreqKeys[i]) < leastVisitedIndex) {
          
        }

      }


      for (var i = lastVisited.length - 1; i >= 0; i--) {
        if (leastFreqKeys.includes[lastVisited[i]]) {

        }
      }
    }
  }
};

/** 
 * 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)
 */

var cache = new LFUCache( 2 /* capacity */ );

cache.put(1, 1);
cache.put(2, 2);
console.log(cache.get(1)); // returns 1
cache.put(3, 3); // evicts key 2
console.log(cache.get(2)); // returns -1 (not found)
console.log(cache.get(3)); // returns 3.
cache.put(4, 4); // evicts key 1.
console.log(cache.get(1)); // returns -1 (not found)
console.log(cache.get(3)); // returns 3
console.log(cache.get(4)); // returns 4