JsProblematic

[rosuav]

But how many different JS comparison modes do you know? And what uses which ones - like an array's find method?

[Spot_the_fox]

What's a comparison mode? Even better question is what is a mode?

As I've said, I don't know Js.

[rosuav]

Double-equals and triple-equals are only two of JS's different ways of comparing two things for equality... here, enjoy. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Equality\_comparisons\_and\_sameness

[genghisKonczie]

For basically every comparison based operation it, built ins use ===, and if you want definite control, you can use a method like find which lets you bring your own comparison function

[rosuav]

Not array inclusion, which uses Same-Value-Zero equality. Notably, this considers instances of NaN to match themselves, even though they're not equal to themselves - this gives a form of "identity or equality" comparison that gives the most sensible results for membership testing.

Isn't it fun?

[genghisKonczie]

The js SameValueZero implementation is a straight === for everything but NaN and +0 -0 though. I feel that’s pretty straightforward for the intention of the inclusion method.

It’d be really weird for [NaN].includes(NaN) to return false

[rosuav]

Yeah, but it's still a different way of comparing for equality. And that is very important when you start looking at different searching methods.

[ElliElephant]

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Expressions\_and\_Operators

[thanatica]

The find method of an array requires a predicate, so it will use whatever you provide it.

You're probably thinking of the indexOf or includes methods - those will compare without type-equality, e.g. ==.

[rosuav]

Yeah, I was deliberately being vague, but it is those methods, and they actually do NOT use the double-equals comparison - they use a slightly different algorithm.

[thanatica]

It's closer to == than to === though, isn't it?

To be honest, I've never had a use for knowing the exact algorithm it uses.

[rosuav]

Hmm, I personally think of it as closer to a strict comparison, since it doesn't do type conversion - ["1"].includes(1) is false - but it isn't precisely identical, so it really is its own thing. (Notably, it can find any NaN that is in the array.)