Boris Zbarsky bzbarsky at MIT.EDU
Thu Mar 6 13:42:12 PST 2014

On 3/6/14 3:58 PM, Domenic Denicola wrote:
>> That would not allow us to kill DOMStringList.
> Can we get more background on DOMStringList?

Sure.  It's used in the following places in Gecko, as far as I can tell:

1) document.styleSheetSets.
2) Microdata API.
3) Various places in indexeddb.
4) The DataTransfer API.
5) Some sort of offline resource list API that's not part of any 
standard I can find.

#1 is not implemented by anyone but Gecko, and the spec is claiming it's 
a DOMString[], which no on implements at all.

#2 is likewise not implemented by anyone but Gecko at this point, and 
the spec likewise claims DOMString[] (which again no one implements).

For #3 I've heard Jonas claim he'd like to just moving ES arrays there.

#4 is specced as a DOMString[], which again no one implements.

I don't know offhand what other UAs do for #3 and #4.

> It seems unlikely that you could get away with replacing a string-only type, which, from the specs I can find, seems to be immutable and have an additional index() method

DOMStringList in Gecko does not have an index() method.  Did you mean 

Whether it's OK to replace with a mutable and any-type-containing thing 
is an interesting philosophical question.  Some of the above use cases 
may be OK with using a frozen array, for example, or not care if the 
page changes it around, since the browser doesn't plan to use it itself.

But yes, it's not a priori obvious that one can replace the other.

> implies it's not implemented in Mozilla

That page was a bald-faced lie.  Note the "in need of a technical 
review" bit.  ;)  I've removed the completely bogus part for now.


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