Null iterable in for-of?

[André Bargull]

Corrected link: https://bugs.ecmascript.org/show_bug.cgi?id=2737


On 6/13/2014 12:16 AM, André Bargull wrote:
>> 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.
>
> for-of statement iteration always ignored undefined/null (always = 
> since it was added in rev6). I've only requested in [1] to align 
> for-of iteration in statements and comprehensions to have the same 
> behaviour w.r.t. undefined/null.
>
>
> [1] https://bugs.ecmascript.org/show_bug.cgi?id=273 

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