iteration order for Object

Brendan Eich brendan at
Mon Mar 14 13:11:38 PDT 2011

On Mar 14, 2011, at 11:02 AM, John Tamplin wrote:

> On Mon, Mar 14, 2011 at 10:21 AM, Brendan Eich <brendan at> wrote:
> Web developers find and exploit many de-facto standards. Enumeration order being insertion order for non-arrays at least, if not for all objects (arrays tend to be populated in index order), is old as the hills and web content depends on it, as far as I can tell. I'll do some experiments to try to get data on this.
> Aside from the JSON example of populating a dropdown list given (which I will agree is a real if contrived use case), there has been a lot of talk of "thousands of web developers" depending on preserving insertion order, but not one concrete example -- do you have one?

We haven't tried changing objects other than "dense arrays" from insertion order, but other browser implementors have. Opera when Lars T. Hansen was working there did, and broke a Wolfenstein port, I believe. Of course they restored compatibility :-).

People in the know at other vendors, please weigh in.

We did try to stop suppressing properties deleted after the for-in loop began, per discussions last May in TC39. That bounced off the web: (see duplicates)


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