Why is NaN not equal to NaN
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Why is this not true?
NaN==NaN
ans =
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Accepted Answer
Cedric
on 16 Jan 2013
Edited: Cedric
on 16 Jan 2013
Most times, you don't want this test to return true indeed. Imagine testing a==b and having a true result when both a and b are undefined; this would make little sense. It is the same with NaN.
While it is not the original question, note that you can test equality assuming NaN 's are equal:
But with that you usually want to test if "behaviors" are the same (and not equality per se), e.g. if two functions return the same number or both NaN do something, else do something else.
More Answers (1)
Matt J
on 16 Jan 2013
Edited: Matt J
on 16 Jan 2013
Because equality is a notion applied to numbers. How can 2 things be equal when they are not numbers?
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math man
on 17 Sep 2021
You might wonder, though, why NaN ~= NaN returns true?
That is, if they are not numbers why are they compared in this case to give a misleading result?
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