Null iterable in for-of?

Brendan Eich brendan at
Thu Jun 12 15:25:55 PDT 2014

Jeff Walden wrote:
> On 06/12/2014 03:05 PM, Allen Wirfs-Brock wrote:
>> >  I believe this behavior for for-in was added in ES5.  My recollection was that Doug Crockford pushed for it.  I don't recall if it was because it matched web reality or simply because he thought it was a good idea.
> It was added for web compatibility, to track what was originally a SpiderMonkey implementation bug, I believe.

Actually, if memory serves, IE JScript tolerated null and undefined on 
right of for-in. SpiderMonkey and my ur-JS implementation, Mocha, did 
not. Someone with the jwz nostalgia Netscape 2/3 browsers, please test.

I don't think bug-hiding precedent trumps bug-finding, personally. Allen?


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