Never the less problem still stands, but maybe there are other ways to solve
it. Only solution I'm left with so far is utility function like this:
function hasRest(f) {
return !!~String(f).split('\n').shift().indexOf('...')
}
Which is bad, specially toString of function is not guaranteed to return source.
Maybe alternative solution could be some standard function / method to test if
the function captures ...rest args.
Regards
--
Irakli Gozalishvili
Web: http://www.jeditoolkit.com/
On Saturday, 2012-06-09 at 23:54 , Allen Wirfs-Brock wrote:
>
> On Jun 9, 2012, at 6:52 PM, Irakli Gozalishvili wrote:
> > I just noticed strange behavior in spider monkey implementation of rest
> > arguments:
> >
> > (function(a, b, ...rest) {}).length // => 2
> >
>
> That answer is consistent with what is specified in the ES6 draft spec. The
> actual value is specified algorithmically and is summarized by this note:
>
>
> NOTE The ExpectedArgumentCount of a FormalParameterList is the number of
> FormalParameters to the left of either the rest parameter or the first
> FormalParameter with an Initialiser. A FormalParameter without an initializer
> are allowed after the first parameter with an initializer but such parameters
> are considered to be optional with undefined as their default value.
>
>
> See section 13.1.
>
> The draft is based upon the conclusions that were reached when this was last
> discussed. See the thread starting
> https://mail.mozilla.org/pipermail/es-discuss/2011-August/016361.html
>
> There is no obviously "right" answer to what should be reported as the length
> (and it isn't clear whether this property really has any utility). The
> closest thing we have to legacy precedent are these statement from previous
> versions of the spec:
>
> 15 Every built-in Function object described in this clause—whether as a
> constructor, an ordinary function, or both—has a length property whose value
> is an integer. Unless otherwise specified, this value is equal to the largest
> number of named arguments shown in the subclause headings for the function
> description, including optional parameters.
> 15.3.5.1 The value of the length property is an integer that indicates the
> “typical” number of arguments expected by the function.
>
> Note that that the the legacy description is not particularly self consistent
> and that where a length value is "other specified" for various built-in
> functions it tends to follow the 15.3.5.1 rule.
>
> Allen
>
>
>
_______________________________________________
es-discuss mailing list
[email protected]
https://mail.mozilla.org/listinfo/es-discuss
