Rails spinoffs - Apr 2008 - Object.isNumber() returns true on NaN??

Hi,

Object.isNumber() returns true on NaN. I don''t think that''s
true....
NaN is Not a Number so it''s not a number... right?

By the way, I''m using Prototype 1.6.0.2.

Satoru
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It depends on your perspective. "typeof NaN" returns
"number" in
JavaScript. NaN certainly doesn''t fit into any of the other buckets.

Others have suggested that NaN ought to make Object.isNumber return
false. But unless we have a compelling reason to do so, I think we
ought to make the function mirror "typeof" as much as possible. Doing
so is, in my opinion, less surprising.

Anyway, if anyone is bothered by this behavior, add something like
this to your standard library:

Object.isValidNumber = function(object) {
  return typeof object === ''number'' && !isNaN(number)
&& number !=Infinity && number !== -Infinity;
};

Cheers,
Andrew



On Apr 11, 3:27 am, Satoru Moriwaki
<satorumoriw...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> Hi,
>
> Object.isNumber() returns true on NaN. I don''t think
that''s true....
> NaN is Not a Number so it''s not a number... right?
>
> By the way, I''m using Prototype 1.6.0.2.
>
> Satoru
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Hi Andrew,

Thanks for your reply.

I understood. I have no problem with your answer.
I''ll extend Object with isValidNumber() method to use it instead :)

Satoru

On Apr 11, 6:18 pm, Andrew Dupont
<goo...-TiabPMV39B5K4mp1Ns0Z8Q@public.gmane.org>
wrote:
> It depends on your perspective. "typeof NaN" returns
"number" in
> JavaScript. NaN certainly doesn''t fit into any of the other
buckets.
>
> Others have suggested that NaN ought to make Object.isNumber return
> false. But unless we have a compelling reason to do so, I think we
> ought to make the function mirror "typeof" as much as possible.
Doing
> so is, in my opinion, less surprising.
>
> Anyway, if anyone is bothered by this behavior, add something like
> this to your standard library:
>
> Object.isValidNumber = function(object) {
>   return typeof object === ''number'' &&
!isNaN(number) && number !=> Infinity && number !==
-Infinity;
>
> };
>
> Cheers,
> Andrew
>
> On Apr 11, 3:27 am, Satoru Moriwaki
<satorumoriw...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
> > Hi,
>
> > Object.isNumber() returns true on NaN. I don''t think
that''s true....
> > NaN is Not a Number so it''s not a number... right?
>
> > By the way, I''m using Prototype 1.6.0.2.
>
> > Satoru
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That''s the beauty of JavaScript!

Satoru Moriwaki wrote:
> I''ll extend Object with isValidNumber() method to use it instead
:)
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That''s what isFinite() does, afaik : )

isFinite(5); // => true

isFinite(''foo''); // => false

isFinite(NaN); // => false
isFinite(Infinity); // => false
isFinite(-Infinity); // => false

- kangax


On Apr 11, 5:18 am, Andrew Dupont
<goo...-TiabPMV39B5K4mp1Ns0Z8Q@public.gmane.org>
wrote:
> It depends on your perspective. "typeof NaN" returns
"number" in
> JavaScript. NaN certainly doesn''t fit into any of the other
buckets.
>
> Others have suggested that NaN ought to make Object.isNumber return
> false. But unless we have a compelling reason to do so, I think we
> ought to make the function mirror "typeof" as much as possible.
Doing
> so is, in my opinion, less surprising.
>
> Anyway, if anyone is bothered by this behavior, add something like
> this to your standard library:
>
> Object.isValidNumber = function(object) {
>   return typeof object === ''number'' &&
!isNaN(number) && number !=> Infinity && number !==
-Infinity;
>
> };
>
> Cheers,
> Andrew
>
> On Apr 11, 3:27 am, Satoru Moriwaki
<satorumoriw...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
>
> > Hi,
>
> > Object.isNumber() returns true on NaN. I don''t think
that''s true....
> > NaN is Not a Number so it''s not a number... right?
>
> > By the way, I''m using Prototype 1.6.0.2.
>
> > Satoru
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