On Apr 18, 2012, at 2:48 PM, Brendan Eich wrote:
> David Herman wrote:
>> *Please*, let's do this right.
> This says to me (what I originally expected) that duplicate property name at
> any ply in an object pattern should be an early error.
>
> Anyone disagree?
I got as far as being ready to type into the spec. the first line to implement
this restriction. Then my reservations flamed-up.
If you think of a destructuring declaration as simply a way to provide the
initial values to a set of declaration is isn't so clear that duplicate
property names are bogus. Consider:
//initialize some variable with default objects
let {
unidentifedAdult: mom,
unidetifiedAdult: dad,
unidentiedChild: brother,
unidentifiedChild: sister
} = peopleConstants;
why is this less desirable than:
//initialize some variable with default objects
let mon = peopleConstants.unidentifiedAdult,
dad = peopleConstants.unidentifiedAdult,
brother = peopleConstants.unidentifiedChild,
sister = peopleConstants.unidentifiedChild;
The former style is less familiar, but is it really "bad" enough to disallow at
the language level?
Disallowing duplicate property names may make sense if you think about
destructuring in ES declarations as pattern matching (which it really isn't)
or a means to break a composite into its constituent parts. But duplicate
properties as initializers for a set of variables seem quite reasonable.
Allen
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