How can I make this regex work on Kotlin/JS the same way it works on Kotlin/JVM? ```fun main() { v...

# getting-started

[Adam S]

How can I make this regex work on Kotlin/JS the same way it works on Kotlin/JVM?

fun main() {
	val r = Regex("""\h+([^:\v]+):""")
    println(r.matchEntire("   Version:")?.groupValues)
    // JVM: [   Version:, Version]
    // JS: SyntaxError: Invalid regular expression: /\h+([^:\v]+):/gu: Invalid escape
}

https://pl.kotl.in/HwXS2Fv3u

EDIT: Ahh, never mind. \h (horizontal whitespace) doesn’t exist in JS. I’ll try replacing it with

[\t\x{00A0}\x{1680}\x{180E}\x{2000}\x{2001}\x{2002}\x{2003}\x{2004}\x{2005}\x{2006}\x{2007}\x{2008}\x{2009}\x{200A}\x{202F}\x{205F}\x{3000}]

(as found on https://regex101.com/)

further suggestions are welcome!

[Johann Pardanaud]

SO suggests [^\S\r\n]+ to replace \h

[Vampire]

An excellent resource when it comes to regex is https://www.regular-expressions.info/.
You can for example easily compare the features of different dialects in the reference.
On https://www.regular-expressions.info/refshorthand.html you would find the \h and see that Java from version 8 on supports it while JavaScript does not.
And on https://www.regular-expressions.info/shorthand.html#more you sould then have a elaborate description and alternatives, so the replacement should be *[*\t\p{Zs}*]. Unfortunately \p... is POSIX class which is also not supported by JavaScript.* 😞

But on https://www.compart.com/de/unicode/category/Zs you can see which characters are part of Zs, so your replacement is almost correct, you just miss space and have additionally the "Mongolian Vowel Separator" which is not part of Zs.

[Johann Pardanaud]

ooooh, thank you Björn! I didn't know there was so much to read on this website. It's good to know for later

[Adam S]

thanks @Vampire, that helps. Unfortunately I’m getting tangled up in other regex differences… it seems like [^\v] doesn’t work consistently

[Vampire]

Of course, \v is as little supported in JS as \h.
[^\v] probably means either "not a `v`" or "neither v nor a backslash"

[Vampire]

https://www.regular-expressions.info/shorthand.html#more is your friend again

[Adam S]

ahh darn, I see

[Adam S]

sure would be nice if Kotlin had a common implementation of a Regex engine, so it was the same on all platforms

[Adam S]

https://youtrack.jetbrains.com/issue/KT-49557

[Vampire]

image.png

[Adam S]

well…. PCRE is written in C. So that could be called from Java and Native, and maybe from JS using wasm?