Map.js

const defineProperty = Object.defineProperty;

/**
 * Initializes an instance of a Map
 * @constructs Map
 */
function Map() {
  /**
   * Object to store the values of the Map
   * @name Map#map
   * @type {Object}
   */
  this.map;

  defineProperty(this, 'map', {
    value: Object.create(null) /* default */
  });

  /**
   * Size of the map
   * @name Map#size
   * @type {number}
   */
  this.size;

  defineProperty(this, 'size', {
    get() { return Object.keys(this.map).length; }
  });


  return this;
}

/**
 * Sets a pair of key, value in the Map
 * @function Map#set
 * @param {*} key 
 * @param {*} value 
 */
Map.prototype.set = function (key, value) {
  this.map[String(key)] = value;

  return this;
};

/**
 * Tells if the Map has a key
 * @function Map#has
 * @param {*} key Key to look for
 */
Map.prototype.has = function (key) {
  return !!this.map[String(key)];
};

/**
 * Deletes a key from the Map
 * @function Map#delete
 * @param {*} key Key to be deleted
 */
Map.prototype.delete = function (key) {
  const result = this.has(key);

  delete this.map[String(key)];

  return result;
};

/**
 * Returns the value of a key in the Map
 * Throws an exception if the key doesn't exist
 * @function Map#get
 * @param {*} key Key to be retrieved.
 */
Map.prototype.get = function (key) {
  return this.map[String(key)];
};

module.exports = Map;