NaN does not equal NaN

Re:NaN does not equal NaN by masklinn on Tuesday September 27, 2011 @04:35PM (#3045106)

You know what's a simple test for NaN? The isNaN built-in function...

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Re:NaN does not equal NaN by simonsarris on Tuesday September 27, 2011 @04:45PM (#3045159)

Yes, but this is bigger than that. JavaScript doesn't define NaN, IEEE-754 defines NaN and JavaScript takes its definition from that. So it's IEEE-754 thinks num == num being false is a good test for NaN.

For the record, isNaN in JavaScript is also not necessarily the fastest way of doing it: http://jsperf.com/nantest

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Re:NaN does not equal NaN by masklinn on Tuesday September 27, 2011 @04:52PM (#3045185)

> For the record, isNaN in JavaScript is also not necessarily the fastest way of doing it

Which will absolutely not matter in 100% of the cases after rounding. `isNaN` is simple (your original criteria) and clearly says what it's doing.

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