lru_cache.js

// https://leetcode.com/problems/lru-cache/

/**
 * @param {number} capacity
 */
var LRUCache = function(capacity) {
  this.cache = new Map();
  this.capacity = capacity;
};

/**
 * @param {number} key
 * @return {number}
 */
LRUCache.prototype.get = function(key) {
  let cache = this.cache;
  let temp = cache.get(key);
  if (temp) {
    // to maintain order
    cache.delete(key);
    cache.set(key, temp);
    return temp;
  } else {
    return -1;
  }
};

/**
 * @param {number} key
 * @param {number} value
 * @return {void}
 */
LRUCache.prototype.put = function(key, value) {
  let cache = this.cache;
  if (cache.has(key)) {
    cache.delete(key);
  } else if (cache.size >= this.capacity) {
    cache.delete(cache.keys().next().value);
  }
  cache.set(key, value);
};

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