hashmap.js

class HashMap {
  
  constructor () {
    this._size = 0;
    this._map = {};
  } 
  
  put (key, value) {
    if (!this.containsKey(key)) {
      this._size++;
    }
    this._map[key] = value;
  },
    
  remove (key) {
    if (this.containsKey(key)) {
      this._size--;
      const value = this._map[key];
      delete this._map[key];
      return value;
    }
    else{
      return null;
    }
  },
    
  containsKey (key) {
   return this._map.hasOwnProperty(key);
  },
    
  containsValue (value) {
    for (var key in this._map) {
      if (this._map.hasOwnProperty(key)) {
        if (this._map[key] === value) {
          return true;
        }
      }
    }
    return false;
  },

  get (key) {
    return this.containsKey(key) ? this._map[key] : null;
  },

  clear (key) {
    this.size = 0;
    this._map= {};
  },

  keys () {
    let keys = [];
    for (let keys in this._map) {
      if (this._map.hasOwnProperty(key)) {
        keys.push(key);
      }
    }
    return keys;
  },

  values () {
    let values[];
    for (let key in this._map) {
      if (this._map.hasOwnProperty(key)) {
        values.push(this._map[key]);
      }
    }
    return values;
  },

  size () {
    return this._size;
  }

}