On Jan 30, 2012, at 6:38 PM, Brendan Eich wrote:
> No! We have a standing agreement to get rid of the awful, lazy-grammar-reuse
> error in ES1 that allows an initializer in for(var x=i in o). We do not want
> this at all for 'let' in either for-in or for-of.
Fine by me, WRT let/const
We haven't done a very good job of capturing such agreements. I don't think
this one is reflected on the wiki proposals...
>
> I think we should break unconditionally and forbid =i in for(var x=i in o)
> too, but that is a separate issue. This botch in grammar factoring is a (bad)
> sunk cost that has zero bearing on the fresh let binding per iteration idea.
> It's terrible anti-precedent. Just say no.
While I think the language would be better without it. I don't really see how
we can justify such a breaking change. Heck, I can even think of a plausible
use:
function hasEnumerableProperties (obj) {
for (var key = false in obj);
return key!==false
}
Allen
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