Are function arguments with the value `undefined` "present"?

David Bruant bruant.d at gmail.com
Fri May 31 07:23:03 PDT 2013


Hi Till,

I believe Boris Zbarski touched on this recently at 
http://lists.w3.org/Archives/Public/public-script-coord/2013AprJun/0428.html 
(I haven't read the full thread, so can't tell what the conclusion were, 
but it's probably worth checking out)

David

Le 31/05/2013 04:33, Till Schneidereit a écrit :
> I couldn't find any precise definition for the spec term "present", so 
> this is not entirely clear to me.
>
> Example:
> In step 7 of 15.4.3.21 Array.prototype.reduce, a TypeError must be 
> thrown if the optional argument `initialValue` isn't present. If a 
> value of `undefined` does *not* cause the argument to be present, that 
> function can be implemented with the following signature:
>
> `function ArrayReduce(callbackfn, initialValue = undefined)`
>
> If, however, the value `undefined` means that the argument is present, 
> the signature should probably be:
>
> `function ArrayReduce(callbackfn, ...rest)`
>
>
> The question isn't entirely academic, as I'm trying to get the 
> self-hosted implementations of builtins in SpiderMonkey to be as close 
> to the spec as possible.
>
>
> thanks,
> till
>
>
> _______________________________________________
> es-discuss mailing list
> es-discuss at mozilla.org
> https://mail.mozilla.org/listinfo/es-discuss

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.mozilla.org/pipermail/es-discuss/attachments/20130531/4eeab432/attachment.html>


More information about the es-discuss mailing list