About invoking JS from Kotlin. Taking the example ...

# javascript

[Vitor Hugo Schwaab]

About invoking JS from Kotlin.
Taking the example of String.prototype.charCodeAt(index).
Is there a way to invoke directly from Kotlin without js(), avoiding the dynamic type?

For example:

val sentence = "The quick brown fox jumps over the lazy dog"
val index = 4
val charCode = js("sentence.charCodeAt($index)")
// charCode = 113

[Piotr Krzemiński]

can you use API provided by Kotlin for the string? I think the equivalent is String.codePointAt

[Piotr Krzemiński]

ah, sorry - it’s available only for the JVM

[Vitor Hugo Schwaab]

Yeah 😞

I was just asking in general, I guess a lot of the Kotlin stdlib isn't implemented in Kotlin/JS and Kotlin/Common yet.
I wonder if adding this kind of functions is something wanted by the Kotlin team.

I'd be happy to raise PRs with this.

[Piotr Krzemiński]

sticking to this particular example for a while, you can achieve what you need with sentence[index].code

[Vitor Hugo Schwaab]

Oh yeah!

I guess String.codePointAt is just the Kotlin/JVM sugar layer.

And Char.code is the Kotlin way of doing things.

A @see [Char.code] in the docs of codePointAt would be awesome 🙂. But I guess if Java changes the codePointAt, this documentation would be broken

[Vitor Hugo Schwaab]

Thanks @Piotr Krzemiński.

[Big Chungus]

Alternatively you can declare your own typesafe global api bindings

[Vitor Hugo Schwaab]

I'm doing something like that.
Multiplatform "String to UTF16BE Byte Array". Super straightforward in iOS, Android and JVM.

But inside the JS function, the dynamic appeared and I was trying to go around it.

So this question came, if there was another way of doing it, or doing something like @Big Chungus suggested.

Good that for this specific case there's indeed a work-around.
But I guess now I know how to proceed in the future. Thanks everyone

[Piotr Krzemiński]

for completeness, the JS API binding would look like this:

@Suppress("NOTHING_TO_INLINE")
inline fun String.charCodeAt(index: Int): Int = asDynamic().charCodeAt(index) as Int

val sentence = "The quick brown fox jumps over the lazy dog"
val index = 3
val charCode = sentence.charCodeAt(index)

maybe it’s possible to do it in a more idiomatic/less noisy way, but this works ☝️

[Big Chungus]

That's not API binding.

[Big Chungus]

I meant external declarations. Although both work.

[Piotr Krzemiński]

Screenshot 2022-11-18 at 12.30.57.png

[Big Chungus]

Yes, you cannot mix externals and extensions