Regular isNaN is very tricky, and almost never what you want: it first coerces i... | Hacker News

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		jefftk on May 10, 2022 \| parent \| context \| favorite \| on: NPM Vulnerability Discussion on Twitter Regular isNaN is very tricky, and almost never what you want: it first coerces its input to a Number, and then checks if that is NaN: `isNaN Number.isNaN ----- ------------ {} true false [true] true false undefined true false "{}" true false`

jaywalk on May 10, 2022 [–]

But none of those things you listed are numbers. The isNaN output is exactly what I want in pretty much every case.

jefftk on May 10, 2022 | [–]

isNaN does not tell you whether something is not a Number either. Applying isNaN to any of these returns false: null, true, false, [], "", "cabbage".

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