ES6 Map Accessor Proxy

MapProxy.js

/**
 * Proxy for accessing ES6 Maps like objects.
 * Usage example:
 * 
 * var p = new MapProxy();
 * p['key'] = 'value';
 * if ('key' in p) {
 *   console.log(p.key);
 * }
 * delete p.key;
 */

function MapProxy(map = new Map()) {
  return new Proxy(map, MapProxy.handlers);
}
MapProxy.handlers = {
  get: function get(map, key) {
    if (map.has(key)) {
      return map.get(key);
    } else {
      return map[key];
    }
  },
  set: function set(map, key, value) {
    map.set(key, value);
  },
  deleteProperty: function deleteProperty(map, key) {
    if (map.has(key)) {
      map.delete(key);
      return true;
    } else {
      return false;
    }
  },
  ownKeys: function* ownKeys(map, key) {
    yield* map.keys();
  },
  has: function has(map, key) {
    return map.has(key);
  },
  enumerate: function* enumerate(map) {
    yield* map[Symbol.iterator || '@@iterator'];
  },
}