The global object in browsers

David-Sarah Hopwood david.hopwood at
Thu Feb 19 02:41:55 PST 2009

Ian Hickson wrote:
> On Thu, 19 Feb 2009, David-Sarah Hopwood wrote:
>> Ian Hickson wrote:
>>> On Tue, 17 Feb 2009, Mark Miller wrote:
>>>> On Tue, Feb 17, 2009 at 5:03 PM, Ian Hickson <ian at> wrote:
>>>>> Indeed, I noted this earlier. The behavior HTML5 codifies is the 
>>>>> behavior that the majority of browser vendors have asked me to codify.
>>>> Majority, huh? Which vendors? How does the behavior they ask for 
>>>> correlate with what their browsers do?
>>> Opera, Apple, and Mozilla. The HTML5 spec originally specced what IE 
>>> does, namely throw an exception when running code whose global object 
>>> doesn't match the current Window object, but Opera, Apple, and Mozilla 
>>> rejected this on the grounds that it could not be implemented in a 
>>> high-performance manner.
>> That is clearly false. It would be a single pointer comparison when 
>> entering a new context.
>> I make no comment here on whether this behaviour would be a good idea on 
>> other criteria, just that rejecting it on performance grounds is absurd.
> To be honest it doesn't really matter to me what the reason is -- if three 
> browser vendors tell me they're not implementing the spec, I change the 
> spec. My goal is to have a specification that browser vendors implement.

I think it should matter. The vendors should be asked to give a reason
that makes technical sense. That this option "could not be implemented in
a high-performance manner" does not make sense -- which means that it is
quite possible that the vendors were asked the wrong question, or had some
misunderstanding about how such a specification could be implemented.

David-Sarah Hopwood

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