Mark S. Miller erights at
Thu Dec 13 20:00:47 PST 2012

On Thu, Dec 13, 2012 at 7:50 PM, Luke Hoban <lukeh at> wrote:
>>> From: es-discuss-bounces at [mailto:es-discuss-bounces at] On Behalf Of John-David Dalton
>>> Subject: Number.isNaN
>>> I noticed that ES6  `Number.isNaN` checks `Type(number)` of Number, would it make sense to instead check that the [[BuiltinBrand]] is BuiltinNumberWrapper similar to `Array.isArray`'s check. This would also allow `Number.isNaN(Object(NaN))` to return `true`. Thoughts?
> The current draft spec [0] uses a ToNumber coercion and checks whether this results is NaN.  So "Number.isNaN(Object(NaN))" will return "true".

In that case, the current spec is wrong. The purpose of introducing
Number.isNaN is to repair the following bug in the global isNaN:

    isNaN("foo") // returns true

> Luke
> [0]
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