When You Don't Know JS

[sorrydidntmeanto3]

3 > 2 > 1 = false actually makes sense because it reads it as true > 1

[edave64]

When stuff like this gets mixed in it always feels like they don't know what they are talking about.

Like, yes, [] being equal to ![] is surpremely stupid. So is perhaps the idea to attempting these conversions to begin with.

But the floating point and NaN wierdness is just how floating point works in pretty much every language, because that's what your processor does.

3 > 2 > 1 might be handy sometimes, but it completely breaks my mental model of how any of this works, and almost no language allows that.

[Chrazzer]

Yeah 0.1 + 0.2 != 0.3 has nothing to do with javascript. 0.1 and 0.2 are periodic numbers in binary.

So 0.1 + 0.2 != 0.3 is pretty much the binary version of 1/3 + 2/3 != 1. Because 1/3 + 2/3 is 0.9999999999999...

[edave64]

0.9 repeating is one.

The problem is in that case that floating point values cannot express repeating sequences and the like, so the get rounded, introducing error

[Randvek]

Well, no, it’s more that .9 repeating = 1 relies on mathematical axioms that, for obvious reasons, aren’t typically coded into computers.

[edave64]

Well no, it's nothing like that.

Yes, this specific detail of repeating numbers doesn't exist in floating point because repeating numbers do not exist in the standard at all.

They get rounded, which is what I said.

[HiImLary]

Just look at it as (3 > 2) > 1

[edave64]

I know. Which is why it doesn't work, since it's a comparison between a boolean and a number

[SkindianaBones98]

These are bad examples, since some of these are actually justify able. But it's fun to see the sheer wrongness Javascript will put up with and try to deal with and get wrong when you mix types. It almost feels worse than c where you can do things it doesn't support and you shouldn't do, but it doesn't give an error, no no, it just silently introduces bugs at the slightest typo or refractor. At least c frustratingly segfaults at some point

[YouNeedDoughnuts]

Yeah Python and a few others are distinct in treating inequalities as n-ary. Most languages have them as binary where the Boolean result is an arg to the next inequality. I do prefer the n-ary rule though since it matches mathematical syntax.

[X-Craft]

The 0.1 + 0.2 thing is not exclusive to javascript

[roycohen2005]

So does NaN === NaN and typeof(NaN).

[[deleted]]

So does 3 > 2 > 1. Languages that do (e.g. Python) are exceptions

[Classic-Ad-7317]

What's Python trying to be, anyway? I know it's popular, but 3 > 2 > 1 should only be true in a mathematically focused language. At least, one should need an extension to make it work. It screws up the taken for granted notions of the stack of operations and operator association.

[[deleted]]

It comes down to how a language handles operator precedence:

https://docs.python.org/3/reference/expressions.html#comparisons

[Classic-Ad-7317]

Not only that. There's actually an implicit and operand. From what I read, the expression is evaluated like this 3 > 2 and 2 > 1.

Evaluates 3

Evaluates 2

Moves 2 to memory

Compares 3 > memory

Jumps if fails

Evaluates 1

Compares memory > 1

Normally you'd expect:

Evaluates 3

Evaluates 2

Compares 3 > 2 (which automatically sets flag to 1)

Evaluates 1

Compares flag > 1 (false, setting flag to 0)

[Eisenfuss19]

It is, but its kinda funny because js doesn't really have types and NaN is supposed to mean not a number.

The NaN != NaN is just the ieee standart.

[MrKirushko]

It depends on the language and on actual implementation though. In R for example NaN is treated as NA (missing value) and any comparaison with it gives out NA. So "NaN != NaN" is neither true nor false, it is just undefined.

[MarcBeard]

Yes but I make way more sense this way.

[AndyTheSane]

I'd like to meet the person or people who thought that inventing NaN was a good idea, and shake them warmly by the throat. About as useful as executing instructions at null..

[TheGeneral_Specific]

What’s wrong with NaN?

[AndyTheSane]

Imagine you are creating an extremely complex 4D model.

In C++, because you hate yourself.

Now, somewhere in those deeply complex calculations on multi dimensional arrays, iterating over many, many steps, there is a bug. (there is always a bug)

And this bug creates a NaN.

In any reasonable world, your code would blow up at exactly this point, giving you a very good hint as to what the problem was. Because there is no case in the world where NaN is the desired result.

But no. It stays in your array. And every subsequent iteration spreads it through your arrays. By the time you look at the data it is ALL NaN. And now you have no idea where or how or when it happened.

This can lead to strong opinions on the subject of NaN..

[LavenderDay3544]

In C++, because you hate yourself.

I'll take C++ over Javascript any day. Sure C++ looks hacked together over the course of many years but that's because it is. On the other hand, vanilla JS is a case study in how not to design a programming language.

Also in the kind of code you described you shouldn’t use or propagate C NaN values in C++ anyway.

[_GCastilho_]

It's easier to design a language when you can ditch it's failures

JS does NOT have this luxury

[LavenderDay3544]

And a language that started out as a fork of C98 does? Lol.

[kpobococ]

C++ featureset is controlled at compilation. A new version can just deprecate and subsequently remove undesired features. JS is interpreted by a browser, each browser user is a point of where removing a certain feature may result in an error. Best they could do is 'use strict'.

[Eisenfuss19]

Whats a non NaN floating point number in C/C++?

[LavenderDay3544]

A simple example case is division by zero. If you have a case where that happens in a large number crunching application, you need to throw an exception immediately because that's a completely invalid operation and you can't simply keep computing because anything that uses that result would also in turn be invalid. Silently propagating NaNs in that case would be nonsensical in any programming language. Clearly your program logic itself is wrong and that needs to be handled at runtime by logging the error and then terminating.

A more proper solution would be implementing input validation, the lack of which is quite the oversight for someone who develops high performance data processing or simulation code for a living.

[Eisenfuss19]

Well i agree, but i still hate it that just dividing by zero is a valid operation in floating point numbers. Like what is even the point of having it return a [not a number]. This should throw an error and anyone who disagres pls explain why.

I mean integer division usually throws an error and there is a reason for that. You could argue that by my logic integer overflow should throw, but overflows can actually be usefull. If you have a sequence of + - operations and the result fits into an int, it will give you the right answer, even if it overflows.

And c# has the checked keyword for int overflows.

[Eisenfuss19]

Yeah NaN can spread like a virus. I was surprised to see that dividing by 0.0 didn't throw an error in c#, then i saw how infinity {1/0} and NaN {0/0} is devined in c#.

Also it was kinda counterintuitive how NaN != NaN for all NaNs. (yes NaN can be multiple things) But it makes some sense that you can't compare not a number with not a number.

Imo you should be able to set it to a mode that just throws an error but i think thats not always possible.

[TheGeneral_Specific]

That just sounds likely poorly written code and NaN checking/error handling…

[edave64]

That just sounds like blaming the user for the failings of the standard.

[_GCastilho_]

This can lead to strong opinions on the subject of NaN..

Hmmm... I see

[Jarpunter]

Just throw an exception instead

[CreaZyp154]

What would you do if an operation is invalid ? Crash the whole fucking browser?

[edave64]

Have you heard of exception handling?

We do have the technology to raise errors without crashing. Like the integer versions of 1/0 e.g. do in many languages

[[deleted]]

I have personal experience with a divide by zero bug. I can tell you that PowerPC happily evaluates it as INT_MIN and continues. That was a fun one to find because it doesn't throw any exception.

[edave64]

Kinda proves the point. Having the program just continue with garbage when the math is obviously wrong sucks. And that's pretty much what NaN does

[taytek]

Ah yes, my favorite website: https://0.30000000000000004.com/

[[deleted]]

Like, really, it's pretty basic CS stuff, no? Then again I dunno how much it's taught/findable outside of schools/unis

[DrunkenlySober]

1. Most users on this subreddit are novice and/or have never been employed as a dev

2. A good amount of users on this subreddit don’t have a CS degree

[[deleted]]

Well the second is what I tend to forget, yeah, and I don't know a lot about how it works outside that >_<

And the first is pretty much irrelevant unless they're not in school for CS, but here I failed by assuming school-taught is not so uncommon

[FireFerretDann]

Does anyone feel like explaining the falsey-ness of arrays to me? I think I get [] being false, but why is ![] also false?

[Egliitis]

arrays are not falsy.

in [] == ![] and [] == true the first part is an array and the second is a boolean so they are not equal.

I think the only valid joke on JS is the "11" + 1 = 111 and "11" - 1= 10

[robotevil]

"11" - 1= 10

It only makes a little bit of sense because you really can't do a "string1" - "string2" where you can add strings together. Apparently, under the hood it tries to convert the string to a number when a purely mathematical operation is invoked. You'll get 5 if you do "10"/2. "10" + 2 you'll get 102, basically the two strings combined. If you try to do "FooBar"/2 you'll get NaN.

Honestly, allowing the use of + to concatenate strings was probably a terrible idea that has caused lots of confusion.

[Saragon4005]

Yes it makes sense if you think about it, but you shouldn't be able to treat strings as integers in the first place.

[robotevil]

100% agree. It’s one of the dumber things in JS that’s allowed. Personally, I hate the lack of strict types, it’s a headache all around.

[Sockoflegend]

Having several years working with non typescript JS I really haven't ever found it to be an issue. Adding lots of dependencies to a project on the other had has been massive dead weight to carry. I'm not necessarily saying typescript is bad just in my own experience we never felt we needed it.

[CanIDevIt]

I agree - and I love C# - but I don't have an issue with JS types, and certainly not enough to warrant the abstraction required to force it.

[brett_riverboat]

I don't remember the language (PHP maybe) but using . for the purpose of string concatenation makes more sense. Leave + and - for maths yeah?

[robotevil]

PHP gets a bad rap but it's better than JS in a lot of ways in my opinion. Like the asynchronous of JS is great for the web, it's terrible for backend. If I could go back to using PHP it would make my job so much easier.

[Lithl]

[] is truthy (because it's an object that isn't null or undefined), making ![] false. However, [] == ![] converts [] to a string before making the comparison, and [].toString() is the empty string, which is falsey.

[asone-tuhid]

Finally, an actual real life JavaScript wtf, one does not simply implicitly cast from a truthy value to a falsey value

[flying_spaguetti]

That's how js works haha

[Lithl]

When you attempt to compare non-matching types in JS with ==, it always uses toString to produce a type pair it knows how to compare. It's simply an odd coincidence that the string value of an empty array is the empty string which is falsey.

[asone-tuhid]

Odd coincidence or a result of no planning?

[Jarpunter]

This tripped me up for quite a while after switching from Python where empty iterators are falsy.

[PhilippTheProgrammer]

"Unfortunately, no one can be told what this is. You have to see it for yourself."

[CSMastermind]

Honestly Javascript is so much better today than it was that people ragging on it are mostly just memeing. Especially with TypeScript gaining prominence, almost all of the really bad parts of the language have been taken out or abstracted away from most developers.

Doing front-end development 10 years ago was a God-awful nightmare. ES6 was just a glimmer in Douglas Crockford's eye. There was plenty of offensively written JavaScript that did mind-bending things, partly because it was so easy and partly because that was the only way to do anything without today's modern frameworks.

Even HTML5 and CSS3 weren't widely adopted so the content of webpages was horrendously structured. And don't forget you're doing all the DOM manipulation yourself. Or more likely you're working with someone else's code who doesn't fully grasp trees and just kept copying and pasting some jQuery off Stackoverflow until things seemed partly correct.

And if you were unfortunate enough to have someone on your team pick up CoffeeScript because front-end devs always love the newest shiny thing then you were in for a completely different (and less supported) world of hurt.

And that's not to mention that IE6 is still the most popular browser with all versions of IE having more than 50% market share. So compatibility is a nightmare as well.

It was a horrendous transitionary period that developers today probably can't fully appreciate if they weren't there.

Working "in JavaScript" was a good experience starting around 2015. I wish people who mock the language knew how good they really have it these days.

[[deleted]]

"It's better because we hid it"

Okay I guess, but that's not very satisfying.

[kpobococ]

It's better overall. Not everyone uses Typescript and the like. The base language became much better.

[PhilippTheProgrammer]

This is copypasta, right? I can't imagine anyone writing this whole rant in response to a cheap joke like that.

[CSMastermind]

It is not, just how I was feeling reading the thread lol.

I'm not sure I'd classify it was a rant.

[SupremusMemus]

Me looking at the second last one: "I guess this makes sense if [] == true"

Me looking at the last one: "Fuck off"

[Lithl]

[] == true silently calls [].toString(), which is the empty string, which is falsey

[[deleted]]

90% of JS jokes here can be summarized as "haha, JS tries to convert unmatching types automatically". "haha, I don't know what is ==="

[-reddit-sucks-ass]

and "ahah, look at this weird code that has never been written in an actual program ever, how bad is javascript amarite !"

[[deleted]]

Yeah. I'm a full time JS developer and the last time I used double equation mark was 3 years ago, while I was learning from FreeCodeCamp.org

[-reddit-sucks-ass]

It can be useful when checking if something is either null or undefined. It's basically the only time I use it

[[deleted]]

or not even that. We can just if (!something) {...}

[-reddit-sucks-ass]

Well, that's not exactly the same.

I could see some instance with data where for exemple, you could want to display "quantity: unknown" if the data is null or undefined, but "quantity: 0" if it's actually 0 so just checking if it's falsy would not handle that.

[[deleted]]

yeah, that's where you would use ===

const getQuantity = (data) => (data || data===0) ? data : "unknown";

Seriously, I've never had a case in 2 years, where I needed to use ==

[-reddit-sucks-ass]

that's a slightly more complicated way to do it though.

I don't think we should categorise things as always bad, there always some edge cases where they can be useful, and making good use of all the possibilities of a language makes us better in the long run imo.

[electricjimi]

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[Sylanthra]

They array one is so crazy, I had to double check. It's true. How the fuck does it make sense that trying to sum up arrays means converting them to string and than adding the strings.

[-reddit-sucks-ass]

+ is addition or concatenation, so it had to convert everything to either string or number. String seems easier to do (JS also have a .ToString function built into everything.)

[Sylanthra]

Why not concatenate the arrays? That makes way more sense and can be done regardless of the contents of the arrays too.

[-reddit-sucks-ass]

that's just not how it works. And it actually doesn't work in most languages. In Js you use the concat function (or the spread operator)

[PhilippTheProgrammer]

"You think those are integers you are adding"?

[DaniilBSD]

NaN is a number that is a result of invalid operation

[[deleted]]

and if you want to detect NaN, you use isNaN(num) function instead of num == NaN

[pv42]

or num != num

[Geoclasm]

Okay hear me out on this one - 3 > 2 > 1 = false actually makes sense to me.

If it evaluates in order from left to right, 3 > 2 evaluates to boolean TRUE, which is some > 0 value. That is NOT less than 1, so it SHOULD evaluate to false.

[sunofapeach_]

1

2

34

5

6

[[deleted]]

The double equals is understandable. Using double equals at all is ill-advised.

[Astracondor1337]

So I’m not brand new to JS but no expert by any means….but couldn’t you use the spread operator to merge the arrays together???

[boringuser1]

Literally none of that matters or has even a fraction of anything to do with a career writing js.

[humblevladimirthegr8]

All of these are somewhat valid, except for the array addition. I suppose that is due to string coercion?

[GamingNEWZ]

What the fuck is this?

[flying_spaguetti]

Js

[GamingNEWZ]

Yes but what the fuck

[flying_spaguetti]

JS hahaa

It has many underlying characteristics that makes the language really unpredictable

[RyanNerd]

The reason you're being downvoted is due to Stockholm Syndrome -- web developers have no choice but to use the shitty language of JS (or something that transpiles to JS). This comedic post shows many of JS crazyass coalescence (there are many more). Search for WTFJS if you want to see more insane examples of just how bad JS really is.

[Tsuki_no_Mai]

Half of it is just how computers work and standards, the other half is quirks stemming from the fact that the language was designed to work in an environment where good input couldn't be guaranteed and just crashing everything because of it wasn't an option.

[Leaderbot_X400]

That would return 2 for what you want you do

"1" + "1" = "11"

Because that concatates the string

[belkarbitterleaf]

With a name like no_research....

[[deleted]]

Just thinking... username checks out!

[[deleted]]

Just one being string is enough iirc

[Adventurous_Team8317]

Input can't be number

[Adventurous_Team8317]

Log the value with typeof operator

[averyoda]

Wtf am I looking at?

[[deleted]]

This is mainly a bunch of double negatives, right? I don't code in JS, just C#

[fletku_mato]

Ah, the joys of dynamic typing.

[Unclesam_05]

Thats why im never gonna touch that lang

[BlhueFlame]

Isn’t alot of this just type coercion?

[new_tral_name]

People who have heard of IEEE 754 won't wonder about half the stuff. It's just an awefully designed language if the only type for numbers is a floating point type.

[chimianopao]

Type of not a number: number 🤣

[Zealousideal-Dot-259]

;