On Jun 12, 2014, at 2:36 PM, Erik Arvidsson wrote:
> Somehow I missed when we decided to allow null/undefined as the iterable
> value in for-of loops.
>
> The following test passes using the spec algorithms:
>
> var c = 0;
> for (var x of null) {
> c++;
> }
> assert.equal(c, 0);
>
> However, if we get a null value here we are most likely just masking an user
> bug.
>
> I assume the justification is that for-in allows null here? However, for-of
> is new syntax and we have the chance to get this right this time around.
Yup, there was an issue that was reported and fixed fairly recently pointing
out that for-of was inconsistent with for-in in this respect.
I agree that treating null/undefined as an empty collection has a smell.
However, in this case my I agree with who ever it was who reported this. that
consistancy between for-in and for-of is what we should have for this condition.
BTW, 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.
Allen
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