Why not NodeList#forEach :\?

Erik Arvidsson erik.arvidsson at gmail.com
Tue Jun 19 15:20:37 PDT 2012

On Tue, Jun 19, 2012 at 1:55 PM, David Bruant <bruant.d at gmail.com> wrote:
> Le 19/06/2012 18:21, Erik Arvidsson a écrit :
>> On Tue, Jun 19, 2012 at 6:42 AM, 程劭非 <csf178 at gmail.com> wrote:
>>> I guess we can try to push Web IDL to do this.
>> WebIDL provides [ArrayClass] and DOM4 make NodeLists ArrayClass. This
>> means that NodeLists have Array.prototype on its prototype chain.
> Excellent! I hadn't heard of that.
>> We tried to make this change in WebKit but it caused some issues,
>> mostly on sites depending on a bug in Closure Library. The Closure bug
>> has been fixed but the question is how many other sites out there do
>> incorrect detection and therefore assume that anything that is an
>> instance of Array is actually a true Array
> I'll guess a quantity between "a lot" and "a ridiculous amount".
> I read "if(something instanceof Array)" very often when view-sourcing
> and they mean "Array.isArray(something)".
> A trickier question is: will this code break the NodeLists inherit from
> Array.prototype and that's harder to answer.

The case that broke was something like this:

if (x instanceof Array)

The problem is that concat behaves different when its argument is a
real Array ([[Class]] is "Array").

I wonder if we could change concat in such a way that it checks the
prototype chain too?


More information about the es-discuss mailing list