code: function each (array, iterator, cb) {
    var len = array.length
    array.forEach(function (item, i) {
      iterator.call(null, item, i, done)
    })
    function done () {
      if (!--len) {
        return cb && cb()
      }
    }
  }
docs: each(array, function (item, i, done) { }, function () { })