EcmaScript koan: NaN is NotANumber. NaN is a number. Object(NaN) is not a number. Thus, Object(NaN) isn't NotANumber.
On Fri, Dec 14, 2012 at 9:22 AM, John-David Dalton <[email protected]> wrote: >> But `myNaN === myNaN` is true if `myNaN = Object(NaN)`. > > That's my point. Normally testing for NaN can be done via `myNaN !== myNaN` > but `Object(NaN)` throws a wrench in that. > It would be great if there was 1 function that was able to detect NaN, > instead of having libs step up and do it. > > -JDD > > > On Fri, Dec 14, 2012 at 9:12 AM, Nathan Wall <[email protected]> wrote: >> >> > Wat? This seems to be a good reason to allow `Object(NaN)` and use the >> > NumberWrapper brand as it cannot be tested via the normal way of >> > `myNaN !== myNaN`. >> >> But `myNaN === myNaN` is true if `myNaN = Object(NaN)`. Testing against >> the object is different. Nothing breaks. >> >> var myNaN = Object(NaN); >> [ 1, 3, myNaN ].indexOf(myNaN); // => 2 >> >> Works as expected. The only problem which occurs is when you're working >> with primitive NaN, in which case the only existing good ways to test for it >> are `x !== x` and `typeof x == 'number' && isNaN(x)`. The purpose of >> `Number.isNaN` is to provide a way to test this case which is easier to read >> and understand. Note that if `x = Object(NaN)` both of these tests fail. >> >> Nathan > > > > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss > -- Cheers, --MarkM _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
