The global object in browsers

David-Sarah Hopwood david.hopwood at
Thu Feb 19 01:39:43 PST 2009

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.

David-Sarah Hopwood ⚥

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