_['each'] = function(collection, iterator) {
  if (Array.isArray(collection) === false && typeof(collection) ===
'object') {
    var values = Object.values(collection);
    var keys = Object.keys(collection);
    for (let i = 0; i < values.length; i++) {
      iterator(values[i], keys[i], collection, i);
    }
  } else {
    for (let i = 0; i < collection.length; i++) {
      iterator(collection[i], i, collection);
    }
  }
}