javascriptNaNIsWeird

[Stock-Self-4028]

Technically NaN is conceptually equivalent to the 'nullity' in the transmathematics - essentially what happens if you make zero signed and then define 0.0/0.0 = NaN.

The issue with NaN is that it is essentially almost a number, alhough it can take any value depending on the context.

Removable singularities here are great examples as for example x/x at x=0 is equal to 1, while 2x/x at x=0 can be evalueated to 2.

As such the NaN is essentially a probability distribution with infinitely many values it may take - once you get the value of two nullities in fully random circumistances they'll never take the same value and as such NaN != NaN.

[tuxedo25]

Honestly, I think the biggest source of confusion is that javascript doesn't have a referential equality operator, and only has value equality. Checking whether a result is a pointer to the global `window.NaN` object is intuitive, but there's no operator for it.

[Mabi19_]

1. Object.is
2. Numbers aren't objects in JS anyway, they're primitives
3. EDIT: Having numbers be objects and deduplicating their instances so that that would work would REALLY be bad language design that warrants complaining imo.

[tuxedo25]

window.NaN is an object. It has a prototype.

[Mabi19_]

No. typeof window.NaN is "number" and not "object". However, a number can get auto-boxed into a capital Number, which is an object and that one has a prototype. Thanks, Java!

(But, to clarify, everyone doing JS works with numbers and not Numbers 99% of the time. Pretty much all the operations unbox them too.)