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What the fuck javascript
(lemmy.nz)
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this post was submitted on 14 Nov 2026
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I think this, and the fact that NaN == NaN is false, make perfect sense.
NaN is the result of mathematically undefined behavior. You’re not going to get a NaN outside of a number context, so tying it together in the Number scope is fine.
It feels silly that a high level language has NaN at all
Same reason NULL != NULL. It makes sense if you understand how these values work.
That doesn't smell right.
https://richiban.uk/2016/12/21/does-null-equal-null/
ISNULL may be true, whilst NULL != NULL. NULL is not a value.
Ah, my brain was in C mode, where NULL is functionally 0. This is about the concept, which doesn't apply equally to all languages.
Yep. There are some languages where this applies, because it’s a mathematical concept. The point is it’s the same ‘no value’ concept, which isn’t ~~shared by~~ implemented the same way by all languages.
C is strongly typed, and uses pointers, so NULL sort of intrinsically has a value in C.
edit: my wording was a bit off
You can kinda think of it as null meaning undefined. In this case, "undefined does not equal undefined" seems easier for me to wrap my head around
The result of mathematically undefined behaviour should be an error, but sure, go ahead and return Keleven. 1/0 = keleven fuck it.
NaN is one of the ways IEEE maths signals an erroneous calculation when the only outbound communication channel is the returned IEEE value. Reading the history and rationale of the floating-point standard will likely convince you this was and probably is a good compromise.
Because IEEE values often have hardware acceleration that is a significant factor in performance, languages rarely (if ever) choose to map all IEEE error values to language-specific error reporting (e.g. a thrown exception or error-tracking algebraic data type).
JS is hardly an outlier here.
I do think it probably violates the principle of least surprise, but I don't think I understand the scale of "momentum" change that would need to take place across society (industry, academia, etc.) to align it with naive expectations.
NaN is a error and it’s your responsibility to handle it gracefully. No need to halt the entire program when you fuck up some maths.
nan is a ieee754-defined error. what javascript calls errors these days (it tends to change a lot) has little to nothing to do with that. it's on every developer to familiarise themself with ieee754, it's one of the most important documents in the profession.
while nan is an invalid floating-point number, it is a valid value for a float-typed field. making it into an error is like adding a bit labelled "crash" to every number in your program.
please do everyone a favor and stop writing code.
Please do everyone an actual favor and stop doing this. You are harmful and toxic.
No, it should not be an error. If you're making a calculator and your user enters 1/0, your program should not have the propensity to crash; the result should simply be NaN and you should choose how you display that result to your user.
error ≠ crash
fault v. error v. failure
In common language they can be synonyms, but often aren't in places (like computing) where there's a useful difference. A page fault isn't an error; a handled error doesn't result in a failure; fault-tolerant systems fail less often than their components fault.
You talk like error handling isn't a thing.
fun fact: getting NaN from a numeric calculation is the error that you handle. if this wasn't obvious, please don't write code for anyone but yourself. hope this helps.
If this wasn't obvious, be glad of the chance to learn.
If we all stopped as soon as something simple wasn't obvious, nobody would learn and nobody would do anything.
What a terrible reply to someone. It cuts off curiosity and says "You are too stupid to do anything."
Yet I bet there was a time that even with that very specific thing, you didn't think of it that way.
NaNis a primitive value, not anError.newcomers to shitting on javascript sometimes learn to blame the tool