@doubledenial | wasteof.money 4

@doubledenial

TIL: In JavaScript, isNaN("") returns false, but parseInt("") returns NaN. o_o

Jul 30, 2022, 5:40 PM

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comments

@nebulous Aug 12, 2022, 7:54 AM

isNaN returns true if the provided object is a Number, and equivalent to NaN.

@doubledenial Aug 12, 2022, 12:26 PM

No, that’s Number.isNaN. The global isNaN, which I used in the post, converts the supplied value to a number if it isn’t already, but it has such odd rules for doing so that the Mozilla web docs have an entire section talking about it.

(Also, “equivalent to NaN" is an odd phrase to use in this context; in JavaScript, NaN != NaN.)

@pkmnq Jul 31, 2022, 2:45 AM

[NaN].includes(NaN) // true
[NaN].indexOf(NaN) // -1

@jeffalo Jul 30, 2022, 10:11 PM

isNaN(parseInt("")) == true

@doubledenial Jul 30, 2022, 11:20 PM

In that case you can use Number.isNaN since you’ll be passing in a number anyway