this post was submitted on 05 Oct 2023
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[–] ICastFist@programming.dev 13 points 2 years ago (3 children)

Javascript, regarding zero, null and undefined = They're all the same thing

[–] Skyhighatrist@lemmy.ca 14 points 2 years ago (1 children)

That's not true these days. You can try it yourself right in your browser's dev console.

These results are from Firefox's console.

0 == null == undefined
> false
0 == null
> false
0 == undefined
> false
null == undefined
> true
null === undefined
> false

And even in the one case where == says they are the same, you can fix that by making sure you are using === so that it doesn't do type coercion for the comparison.

[–] shrugal@lemm.ee 2 points 2 years ago* (last edited 2 years ago) (1 children)

Shhhhh, bashing Javascript is cool around here.

[–] JackbyDev@programming.dev 1 points 2 years ago (1 children)

Just make fun of it for having two flavors of null.

[–] shrugal@lemm.ee 2 points 2 years ago (1 children)

So what's wrong with having two flavors of null?

[–] JackbyDev@programming.dev 2 points 2 years ago (1 children)

It's super confusing. A lot of people think even one null is a problem.

[–] shrugal@lemm.ee 2 points 2 years ago (1 children)

What's confusing about that? It's null, just two different kinds with slightly different meanings. Is having two boolean values also confusing?! Should we simplify it?

I mean I can get behind trying to remove null entirely and replacing it with better concepts, but I cannot understand why having one more null value suddenly makes it confusing. You don't even have to care in 95% of the cases, and it can be useful in the other 5%.

Honestly, it looks more like some kind of misguided purism to me.

[–] JackbyDev@programming.dev 1 points 2 years ago (1 children)

Why stop at two? Why not have a dozen versions of null?

[–] shrugal@lemm.ee 1 points 2 years ago* (last edited 2 years ago)

Idk, how many more do you need?

[–] ryan@the.coolest.zone 8 points 2 years ago (1 children)

Oh man, you've got me itching to get into the intricacies of JavaScript...

One fun example of the difference: when doing arithmetic operations, null is indeed converted to 0, but undefined is converted to NaN. This has to do with null being an assigned value that represents empty, whereas undefined is not actually a value but a response indicating that there was no value assigned in the first place.

[–] dan@upvote.au 7 points 2 years ago* (last edited 2 years ago) (1 children)

response indicating that there was no value assigned in the first place.

You can explicitly assign undefined to a variable though.

Another fun fact about JavaScript is that undefined never used to be a keyword. If you did var foo = undefined, foo would indeed have a value of undefined, but it was only because there was no variable called undefined in scope!

You could do var undefined = 42 then var foo = undefined would actually set foo to 42! window.undefined = 42 would break all sorts of things.

Thankfully this was fixed with ES5 in 2009, although it took a few years for browsers to make the change.

[–] darcy@sh.itjust.works 4 points 2 years ago

javascript moment

[–] DarkenLM@artemis.camp 1 points 2 years ago

Reminds me of this trifecta.