"Subclassing" basic types in DOM - best method?
Tab Atkins Jr.
jackalmage at gmail.com
Tue Nov 20 11:45:58 PST 2012
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. It suffers
from cross-frame issues, but shrug. Similar checks will proliferate
as people write methods that take generic Maps.
(On the other hand, they might instead just feature-test for the
existence of items(), and then use it as an iterable, in which case
this would be a non-issue. Depends on the use-case, I suppose.)
> Where I would like to go, if you force me to pick a promising path:
That's my preferred direction, too, but I suspect that's far off. It
doesn't even have a strawman yet, does it?
More information about the es-discuss