- From: Boris Zbarsky <bzbarsky@mit.edu>
- Date: Tue, 13 Jan 2015 13:22:43 -0500
- To: Ryosuke Niwa <rniwa@apple.com>, Domenic Denicola <d@domenic.me>
- CC: Anne van Kesteren <annevk@annevk.nl>, WebApps WG <public-webapps@w3.org>, "www-dom@w3.org" <www-dom@w3.org>
On 1/13/15 1:18 PM, Ryosuke Niwa wrote:
> I agree. It's unusual for a constructor of a super class to automatically instantiate an arbitrary subclass based on its arguments. And we usually solve that convenience problem by introducing a factory class/function.
While true, I do think there's a problem here. Consider this:
var element = new HTMLElement("somename");
OK, so the web author is not being very forward-compatible in that
they're not using a tag name with a "-" in it. But then they put it in
the DOM and it acts just like a span, and they're happy with that.
Then we want to add a "somename" tag in the spec, and suddenly this JS
throws. This is a different order of breakage than what you get from
just having new semantics for the "somename" tag.
In some cases, this is a problem no matter what; e.g. if "somename" is
actually "img" or "canvas" then the layout is totally different too, not
just the semantics. But there are other cases where the layout is not
that different from a vanilla inline.... though maybe we don't really
plan to add any more of those?
In any case, it's a bit of a niggling worry for me because it can
increase the chance that adding things to HTML breaks websites.
-Boris
Received on Tuesday, 13 January 2015 18:23:14 UTC