LeetCode 146. LRU Cache (javascript solution)

Description:

Design a data structure that follows the constraints of a Least Recently Used (LRU) cache.

Implement the LRUCache class:

LRUCache(int capacity) Initialize the LRU cache with positive size capacity.
int get(int key) Return the value of the key if the key exists, otherwise return -1.
void put(int key, int value) Update the value of the key if the key exists. Otherwise, add the key-value pair to the cache. If the number of keys exceeds the capacity from this operation, evict the least recently used key.

Solution:

class LRUCache {
  constructor(capacity) {
    this.cache = new Map();
    this.capacity = capacity;
  }

  get(key) {
    if (!this.cache.has(key)) return -1;

    const v = this.cache.get(key);
    this.cache.delete(key);
    this.cache.set(key, v);
    return this.cache.get(key);
  };

  put(key, value) {
    if (this.cache.has(key)) {
      this.cache.delete(key);
    }
    this.cache.set(key, value);
    if (this.cache.size > this.capacity) {
      this.cache.delete(this.cache.keys().next().value);  // keys().next().value returns first item's key
    }
  };
}