An update on Object.observe

Brian Chin brianchin at google.com
Mon Nov 2 19:35:00 UTC 2015


Regarding the Polymer 1.0 situation, as a client the new system seems to be
simpler. The core aspect is that now when you modify a property, the
resulting changes propagate instantly. O.o required update callbacks to be
executed on a new microtask after the associated field/item was modified.
In my experience, the instant propagation is easier to reason about for the
end user.

On Mon, Nov 2, 2015 at 11:31 AM, Benoit Marchant <marchant at mac.com> wrote:

> Hi Adam,
>
> Just sharing my $0.02 : I implemented a two-way binding system in my first
> JavaScript framework at Apple in 2007, designed as a layer on top of a
> property change observing API, like in Cocoa, and that’s still our design
> in Montage today. I’ve never felt the need nor understood why observing
> changes on a whole object were useful for bindings, and without measuring,
> I was concerned (maybe wrongly) by the performance overhead of doing so.
>
> Thanks for the update.
>
> Benoit
>
> On Nov 2, 2015, at 10:27 AM, Adam Klein <adamk at chromium.org> wrote:
>
> Over three years ago, Rafael Weinstein, Erik Arvidsson, and I set out to
> design and implement what we believed to be the primitive underlying the
> data-binding system of MDV ("model-driven views"). We prototyped an
> implementation in a branch of V8, then got agreement from the V8 team to
> build a real version upstream, while pushing Object.observe ("O.o") as a
> part of the upcoming ES7 standard and working with the Polymer team to
> build their data-binding system on top of O.o.
>
> Three years later, the world has changed in a variety of ways. While other
> data-binding frameworks (such as Ember and Angular) showed interest, it was
> difficult to see how they could evolve their existing model to match that
> of O.o. Polymer rewrote from the ground up for its 1.0 release, and in that
> rebuilding did not utilize O.o. And React's processing model, which tries
> to avoid the mutable state inherent in data-binding systems, has become
> quite popular on the web.
>
> After much discussion with the parties involved, I plan to withdraw the
> Object.observe proposal from TC39 (where it currently sits at stage 2 in
> the ES spec process), and hope to remove support from V8 by the end of the
> year (the feature is used on 0.0169% of Chrome pageviews, according to
> chromestatus.com).
>
> For developers who have been experimenting with O.o and are seeking a
> transition path, consider using a polyfill such as
> https://github.com/MaxArt2501/object-observe or a wrapper library like
> https://github.com/polymer/observe-js.
>
> - Adam
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