Iterator current/prev value

Brendan Eich brendan at
Sun Mar 23 11:24:34 PDT 2014

Marcus Stade wrote:
> This is assuming that the `current` or `prev` property is indeed 
> implemented by the engine and not user land, as that indeed both 
> carries implementation cost and the risk out running out of sync. Is 
> there any way other than generator functions to implement iterators? 
> Are any ol' object with a function called `next` an iterator?

Any old object. It's a structural or "duck-typed" protocol.

We won't therefore be adding complexity, which is also bad on its own. 
KISS wins here. More elaborate protocols for harder or let's say rarer 
cases are fine and not part of the mandatory minimum.


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