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Maybe we should think about Interface.isInterface functions again

From: Boris Zbarsky <bzbarsky@MIT.EDU>
Date: Fri, 19 Jul 2013 23:46:30 -0400
Message-ID: <51EA0816.5010101@mit.edu>
To: "public-script-coord@w3.org" <public-script-coord@w3.org>
I've brought this up before: there is nothing in the DOM that allows 
reliably detecting DOM objects that implement a given interface. 
Something like Array.isArray or ArrayBuffer.isView as defined in ES.

Last time this came up we had sort of agreed to make instanceof kinda 
work for this by making it consider brands in addition to proto chains, 
but this has a problem: HTMLElement.prototype instanceof Node is very 
much true (and web pages depend on this behavior, as I recall) but 
HTMLElement.prototype is most definitely not something that would pass a 
sane isNode() check...

Now I suppose spec authors could add such things ad-hoc (e.g. add a 
"static boolean isNode(any arg)" on Node and define it in prose to 
return true if and only if arg is a Node).  But maybe there should be a 
way to either express this in IDL or the default behavior should be to 
have such methods?

-Boris
Received on Saturday, 20 July 2013 03:46:59 UTC

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