alternative interface

[pfraces]

Iterators are functions which iterate data returning each iteration as { value, index } (being index optional) each time is called and undefined when no more iterations are available

var iterator = arrayIterator([1, 2, 3]);
iterator(); // { value: 1, index: 0 }
iterator(); // { value: 2, index: 1 }
iterator(); // { value: 3, index: 2 }
iterator(); // undefined

[pfraces]

var arrayIterator = function (array) {
  var length = array.length;
  var index = 0;

  var iterator = function () {
    if (index === length) { return; }
    var iteration = { value: array[index], index: index };
    index = index + 1;
  };

  return iterator;
};

[pfraces]

var each = function (iteratee, iterator) {
  var iteration = null;

  while (iteration = iterator()) {
    iteratee(iteration.value, iteration.index);
  }
};

[pfraces]

Async variant

var iterator = arrayIterator([1, 2, 3]);

iterator(function (value, index) {
  // ...
});

With this variant it makes no sense to implement an each method for iterators since the iterator itself is enough

It supports both, sync and async variants and the standard array/object iterators can get an additional parameters like async: true or the number of iterations in a tick...