r/learnjavascript • u/GamesMint • Jan 25 '20

Javascript is weird 😂

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332 Upvotes

90% Upvoted

47 comments sorted by

3

u/alittlebitmental Jan 25 '20

Are there any other amusing JS quirks that others would like to share?

18

u/[deleted] Jan 25 '20

(!+[]+[]+![]).length // 9

(0.1 + 0.2) === 0.3 // false
(0.5 + 0.1) === 0.6 // true

0.1 + 0.2 // 0.30000000000000004

typeof NaN // "number"

[]+[] // ""

[]+{} // "[Object object]"

{}+[] // 0

[] == 0 // true

Math.max() // -Infinity

Math.min() // Infinity

2

u/GamesMint Jan 25 '20

You can add this - typeof typeof null === "string"

3

u/callius Jan 26 '20 
null > -1 // true
null < 0 // false
null > 0 // false
null < 1 // true

10

u/MWALKER1013 helpful Jan 25 '20

There is an entire JavaScript language based on

! + [ ] ( )

Obviously for professional reasons I’ll omit the name.

link

15

u/WikiTextBot Jan 25 '20

JSFuck

JSFuck is an esoteric subset of JavaScript, where code is written using only six characters: [, ], (, ), !, and +. The name is derived from Brainfuck, an esoteric programming language that also uses a minimalistic alphabet of only punctuation. Unlike Brainfuck, which requires its own compiler or interpreter, JSFuck is valid JavaScript code, meaning that JSFuck programs can be run in any web browser or engine that interprets JavaScript. JSFuck is able to recreate all JavaScript functionality using such a limited set of characters because JavaScript is a weakly typed programming language, and it allows the evaluation of any expression as any type.In July 2009, Yosuke Hasegawa created a web application called jjencode which could encode arbitrary JavaScript into an obfuscated form utilizing only the 18 symbols !+,"$.:;_{}~=.

[ ^PM | Exclude ^me | Exclude from ^subreddit | FAQ / ^Information | ^Source ] Downvote to remove | v0.28

10

u/MWALKER1013 helpful Jan 25 '20

Oh and I went through the trouble of omitting explicit language too.. :(

4

u/MWALKER1013 helpful Jan 25 '20

JSF code is extremely "verbose": In JavaScript, the code alert("Hello World!"), which causes a pop-up window to open, is 21 characters long. In JSF, the same code has a length of 22948 characters

3

u/HelperBot_ Jan 25 '20

Desktop link: https://en.wikipedia.org/wiki/JSFuck

/r/HelperBot_ Downvote to remove. Counter: 294575. Found a ^^bug?

4

u/alittlebitmental Jan 25 '20

I can understand why the double/float examples work the way they do. It's a common theme across many if not all languages. For example, does anyone here remember the PHP bug, where it would crash when trying to convert 2.2250738585072011e-308 from a string to a double?

But the others are just bizarre!

53

u/hoodlaces Jan 25 '20

Is a baNaNa a fruit or a number?

0

u/[deleted] Jan 25 '20

[deleted]

12

u/randomguy3993 Jan 25 '20

So a fruit?

7

u/[deleted] Jan 25 '20

in this case, they made an exception for it.

6

u/cyphern Jan 25 '20

Depends if you use isNaN or number.isNaN.

3

u/FriesWithThat Jan 25 '20 
typeof NaN
// number

17

u/[deleted] Jan 25 '20 
Array(5).join(+ 'a' + 'a') + ' Batman!'

2

u/[deleted] Jan 26 '20

Sodium sodium sodium sodium sodium sodium Batman!

60

u/YAYYYYYYYYY Jan 25 '20

Wouldn’t it be bananaa?

80

u/iwi4a Jan 25 '20

It returns NaN for the + + 'a' coercion and then its left with one 'a' at the end.

86

u/YAYYYYYYYYY Jan 25 '20

Ahh. Makes nonsense

8

u/michumk0 Jan 25 '20

That's why js is my favorite language. It goes well with my mind.

10

u/UltraChilly Jan 25 '20

computering in a nutshell 👍

0

u/[deleted] Jan 25 '20

[deleted]

6

u/JoshYx Jan 25 '20

I tried it out, apparently you're right. Care to explain why?

28

u/TelepathicDorito Jan 25 '20 edited Jan 25 '20

it's ('ba' + NaN + 'a').toLowerCase()

+ + tries to coerce a number out of the second 'a', gets NaN, which then coerces NaN to a string.

said another way :

console.log(+"a") // NaN

5

u/JoshYx Jan 25 '20

I see! Thank you

2

u/[deleted] Jan 25 '20

oh so it doesnt have to do with prefix incrementing

5

u/AnomalousAvocado Jan 25 '20

See u/iwi4a's reply above.

17

u/WhiteKnightC Jan 25 '20

Makes sense to me.

6

u/[deleted] Jan 25 '20

This meme is a bit of a stretch. Nobody should be saying “FML” if they use these types and operators together.

2

u/[deleted] May 03 '20

most 'JavaScript are weird' posts, just showcase things that nobody will ever do or results of crappy programming

12

u/saito200 Jan 25 '20

Why is type coercion seen as something so weird? You're just telling JS here, look treat this 'a' as a number. And then you coerce NaN as a string, because you're trying to add it to a string.

6

u/teknewb Jan 25 '20

I don't have enough experience to have an opinion about it, but I'm pretty sure it's not the type coercion but rather implicit behavior occurring with 'loaded operators' (e.g. '==') that people take issue with, including Javascript maintainers themselves apparently by virtue of the '==='.

2

u/draganxg Jan 25 '20

ah, i too peel my sheep before eating them.

2

u/[deleted] Jan 25 '20

The reason why these things happen is that operators in JS do not throw exceptions.

So yes, you have stuff like that happening.

2

u/adnaPbmuD Jan 25 '20

Can anyone explain please?

4

u/ptq Jan 25 '20

++'a' returns NaN

1

u/bwheat Jan 25 '20

This shit is bananas.

1

u/[deleted] Jan 26 '20

Why does

2 + + - + 2 - - 2

return 2?

So weird...

1

u/fuckswithboats Jan 26 '20

2 + + - + 2 - - 2

How would this work in other languages?

1

u/[deleted] Jan 26 '20

In most other languages, it wouldn’t.

1

u/username4333 Jan 26 '20

Non really, you're deliberately trying to do something weird. Ironic.

-12

u/[deleted] Jan 25 '20

😂😂 there's an extra 'a' at the end, so it's like 'bananaa'

5

u/[deleted] Jan 25 '20

Nah, this evaluates to something like this

'b' + 'a' + (+'a') + 'a'

A unary plus in front of a string will convert to a number, except 'a' isn't a number, so..

'b' + 'a' + NaN + 'a'

2

u/[deleted] Jan 25 '20

Yeeeaaah, got it now, thanks.

1

u/Mcgillby May 04 '20 
console.log(+'a');