Mark S. Miller wrote:
On Fri, Aug 17, 2012 at 6:49 PM, Brendan Eich <[email protected]
<mailto:[email protected]>> wrote:
All praise to Raf et al., my concern is that something
synchronous, plus event loop concurrency and setImmediate, would
suffice to bootstrap the rather more elaborate proposal on top of
the simpler O.p.watch like fundament.
This is not to say we shouldn't standardize higher-level APIs, and
instead push that off on library authors to write, and users to
download. There's a delicate balance here. We often screw up
higher-level abstractions in annoying ways, but perhaps that risk
is worth taking.
What I'm really getting at is this: why not expose the synchronous
primitive and e.l.c. building blocks as well?
A synchronous observation mechanism provides an attacker too many
opportunities for a plan interference attack. If you'll recall, an
earlier synchronous proposal died for this reason.
Thanks, I recall -- but this needs to be stated clearly in the spec. I
hear from people all the time asking Y U no Object.prototype.watch.
/be
Object.observe has been carefully designed to strike a good balance
between providing non-malicious code useful new powers without
providing attackers significant new attack opportunities. The core
principle is that a client of an object can anyway observe changes to
observable state asynchronously by polling between turns. And a client
of an object, if it receives control during a turn, can poll while it
has control. To a first approximation, Object.observe can be
understood as an optimization of polling. It is actually more powerful
than that, but in ways that are beneficial without IMO creating
significant new hazards.
/be
Brandon Benvie wrote:
I agree on the above with regard to Proxies. They are awesome
and allow for incredible things, but Object.observe fills a
different use case that I think is more common at at the user
standpoint or at least library standpoint. When you look
around at the major JS libraries that exist the problem they
are trying to solve (after DOM normalization) is data-binding.
Proxy can be used to solve this for new objects or wrapped
objects, but that's overkill and may have performance
consequences, and has no support for working with existing
objects. Proxy and observe end up filling two completely
different use-cases, and I would venture to say that observe
is the one that most people could make better use of if they
had it in their hands today.
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--
Cheers,
--MarkM
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