[Spawning new thread on public-script-coord; whatwg to bcc]

From: whatwg <whatwg-boun...@lists.whatwg.org> on behalf of Jonas Sicking 
<jo...@sicking.cc>

> On Wed, Aug 20, 2014 at 1:33 AM, Anne van Kesteren <ann...@annevk.nl> wrote:
>> On Wed, Aug 20, 2014 at 10:29 AM, Jonas Sicking <jo...@sicking.cc> wrote:
>>> FWIW, the web platform sorely needs a construct for "readonly state
>>> variable + event whenever the state changes". I.e. some form of
>>> observable which remembers the last produced value. I had hoped the
>>> Streams would get us closer to that, but the current definition seems
>>> to be too different.
>>
>> Isn't that Object.observe() with custom records produced by the
>> specific object you are defining for the property you want to enable
>> this for (in this case held, it seems like)?
>
> That's a good question. It'd be awesome if Object.observe() solved this 
> problem for us.
>
> One thing that I'd worry about is that it'll be hard for authors to know 
> which properties are observable, and which ones aren't. But maybe that's 
> something we can live with.

Object.observe() is in my mind exactly what solves this problem.

Remember that it doesn't work out-of-the-box for getters. And, most DOM 
properties are clearly "getter-like" from an author perspective: i.e., besides 
that being their actual observable implementation, they also are usually 
getting some underlying part of the system that is not otherwise accessible; it 
is hard to imagine them as simple data properties which anyone can toggle. So 
IMO authors will bring the same expectations to DOM objects they do to regular 
objects: getters will be sometimes observable, but only if the implementation 
of that object has taken the time to make them so.

I think it would be a good idea to start working on additions to WebIDL to mark 
properties as observable, so that Chrome at least can start firing change 
records for them. I imagine this propagating to developer docs (MDN etc.) as 
some kind of "observable" annotation that authors will come, in time, to learn 
means they can Object.observe() that property.

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