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Which of these javascript expressions is false? (lemmy.ml)

submitted 6 days ago by cm0002@lemmy.world to c/programmer_humor@programming.dev

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[-] powermaker450@discuss.tchncs.de 16 points 6 days ago

C, because yes.

[-] Valmond@lemmy.world 8 points 6 days ago

I'd say C too because that's the only one that would be True in a normal programming language and this is javascript so...

[-] powermaker450@discuss.tchncs.de 4 points 6 days ago

probably not true in most other langauges. although I'm not well versed in the way numbers are represented in code and what makes a number "NaN", something tells me the technical implications of that would be quite bad in a production environment.

the definitive way to check for NaN in JS would probably be something like

// with `num` being an unknown value

// Convert value to a number
const res = Number(num);

/*
 * First check if the number is 0, since 0 is a falsy
 * value in JS, and if it isn't, `NaN` is the only other
 * falsy number value
 */
const isNaN = res !== 0 && !res;

[-] Remavas@programming.dev 2 points 3 days ago

NaN is a special floating point value. https://en.wikipedia.org/wiki/IEEE_754

It's weird but it makes sense why it was chosen to be this way.

[-] Remavas@programming.dev 4 points 6 days ago

It's not true in a normal programming language. If it is true in yours, you should stop using it immediately.

[-] Valmond@lemmy.world 1 points 6 days ago

A non type should be a type. It should be of the type none. And it is in good script languages like Python so I don't know why you think it shouldn't.