Mike Shaver wrote:
> On Sun, Mar 23, 2008 at 2:44 AM, Dean Edwards <[EMAIL PROTECTED]> wrote:
>> I'd prefer Array.forEach(null) to do nothing, just like for (var i in
>> null) does nothing. I'm prepared to be convinced otherwise. :-)
>
> forEach isn't like enumeration, though, it's like the more common
> Array pattern of
>
> for (var i = 0; i < a.length; i++) {
> doIt(a[i]);
> }
>
> And if a is |window|, you get exactly the same effects, no? If a is
> null, you get an exception, which I think is probably not what we
> want. FWIW, ES3 specifies that |for (var i in null)| throw a
> TypeError (see 12.6.4 step 3, and 9.9), but we and AFAIK all other
> browsers intentionally diverge; we made that change relatively
> recently, I think in FF2's timeframe. I expect that ES4 will specify
> the non-throwing behaviour, because an exception is just too harsh a
> punishment for trying to iterate over null or undefined.
>
Like I said previously, Array.generic delegating to
Array.prototype.generic.call is an artefact of the way JS grew as a
language. Generics were added later. If generics were originally
specified then Array.prototype.generic would delegate to Array.generic.
From the ES4 reference implementation Array.es:
prototype function forEach(eacher, thisObj=null) {
Array.forEach(this, eacher, thisObj);
}
It seems we have three choices for Array.forEach(null)
1) Do nothing
2) Throw an exception
3) Use the current object and iterate that
I prefer the first one, throwing an exception is acceptable too but the
last one is counter-intuitive IMO.
-dean
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