Would "an array-like with a negative length field" read better in
ecmaspeak? I'm talking about the value *before* ToLength is invoked.
`Array.prototype.slice.call(3)` and
`Array.prototype.slice.call({length:-1})` both complete successfully (and
return the same value), due to the soothing effect of `ToLength`. My
informal definition for "array-like" is "something which is not actually an
Array but which will not throw an error when used as the receiver in an
invocation of a generic method of Array", so both `3` and `{length:-1}` are
"array-like" under my definition, and then I need a way to describe the
difference between them. I believe you are saying they are both
"array-likes with zero length", since that's the result of ToLength. But
perhaps you wouldn't call them "array-like" at all?
--scott
On Feb 14, 2014 3:12 PM, "Claude Pache" <claude.pa...@gmail.com> wrote:
>
>
> > Le 14 févr. 2014 à 23:40, "C. Scott Ananian" <ecmascr...@cscott.net> a
> écrit :
> >
> > Claude Pache wrote:
> >> "Array-likes with negative length" doesn't make sense.
> >
> > `Array.prototype.copyWithin.call({ length: -1 }, ... );`
> >
> > Call it whatever you like, although I'm always interested in learning
> > new phrases of ECMAspeak (if there's an appropriate name for this).
> > --scott
>
> Since you are interested: "The abstract operation ToLength converts its
> argument to an integer suitable for use as the length of an array-like
> object." [1]
>
> It doesn't really matter whether ToLength could extract a reasonable value
> for an unreasonable object, or not. But consistency is important: note that
> this operation is used whenever the length of an arraylike is expected, not
> only for default arguments.
>
> [1] http://people.mozilla.org/~jorendorff/es6-draft.html#sec-tolength
>
> —Claude
>
>
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