"Subclassing" basic types in DOM - best method?
Peter van der Zee
ecma at qfox.nl
Tue Nov 20 13:54:17 PST 2012
On Tue, Nov 20, 2012 at 10:31 PM, Rick Waldron <waldron.rick at gmail.com> wrote:
> On Tue, Nov 20, 2012 at 2:45 PM, Tab Atkins Jr. <jackalmage at gmail.com>
>> On Mon, Nov 19, 2012 at 9:46 PM, Brendan Eich <brendan at mozilla.com> wrote:
>> > Tab Atkins Jr. wrote:
>> >> If we did this, the only reason to continue subclassing Map is to get
>> >> instanceof checks to work. Is this acceptable?
>> > I think it's either irrelevant (no one tests 'aUrlQuery instanceof Map')
>> > or else a potential problem (cross-frame instanceof).
>> People *do* perform those checks, though. For example, in a method
>> that accepts either an array or other things, a quick "foo instanceof
>> Array" check is a clear, easy way to check what you've got.
> Be careful there, it's incredibly rare to see code that does that—which is
I don't agree. I see often see instanceof, both with Array and with
other objects. This danger you and everybody speaks of only applies to
cross-frame scripts. And while this danger is real (and I don't mean
to make it sound like it isn't), I think you should first consider the
amount of people actually doing cross frame scripting because it's not
something most people touch frequently, if at all. Any studies to get
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