New ES6 draft now available

Tom Van Cutsem at
Tue Nov 27 06:19:00 PST 2012

2012/11/26 Allen Wirfs-Brock <allen at>

> On Nov 26, 2012, at 10:56 AM, Tom Van Cutsem wrote:
> I'm skeptical though, whether this change achieves your original goal of
> reducing the risk of inconsistencies between the different operations. It
> depends on whether you think doing a case-analysis using switch or if-tests
> is less error-prone than having to override/implement multiple different
> traps.
> Yes, I do think case analysis in a single function is less error-prone. I
> think logic that is centralized to a single function is more likely to
> self-consistent than logic that has to be duplicated in multiple functions.
>  Particularly, when it is possible to redefine the multiple functions
> individually without being forced to redefine the entire set.

It's all a matter of trade-offs. One thing that we lose by bundling
everything into a single trap is the ability to easily add new traps with
default semantics. One of the reasons for baking the Handler API into the
spec was that we could add new derived traps in ES7+, and Proxy
abstractions whose handler subclasses Handler would inherit a sensible
default implementation of these new derived traps.

When dealing with a getIntegrity/setIntegrity trap, it's not easy to add a
new object state later: the existing case-analysis code won't be prepared
to deal with it.

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