Object.prototype.filter = function(fn) {
  return Object.keys(this)
    .filter( key => {
      const result = fn(key, this[key], this);
      return result === false || result === null;
    })
    .reduce((obj, key) => Object.assign(obj, {[key]: fn(key, this[key], this)}),
            {});
}

Object.prototype.map = function(fn) {
  return Object.keys(this)
  .reduce((obj, key) => Object.assign(obj, {[key]: fn(key, this[key], this)}),
          {});
}