Check out Dart's iterators

Domenic Denicola domenic at
Sat Feb 9 23:54:25 PST 2013

I know `StopIteration` is pretty baked in by now. But, most of the arguments I can recall for it are that it’s better than `hasNext` + `next`, wherein you have to keep two methods in sync. I saw the Dart iterator API the other day and it provided a third alternative I thought the list might enjoy contemplating:

Translated to ES6, an iterable that counts to 5 it would look like:

import { current, next } from "@iter";

let iterable = {
  [next]() {
    if (this[current] < 5) {
    return this[current] <= 5;
  [current]: 0

That is, `next` does all the work, returning `true`/`false` to signal whether the iteration should proceed. It then keeps `current` in sync with the current value.

Interesting, if perhaps too late for ES6. I'd of course love to hear why `StopIteration` is better than this, so I can understand and defend it better.

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