I'm trying to have such a function in Wasm target ...

# webassembly

[Piotr Krzemiński]

I'm trying to have such a function in Wasm target (it works fine for other targets):

internal actual fun isInteger(value: Any): Boolean =
    js("return Number.isInteger(value)")

but I'm getting Type 'Any' cannot be used as value parameter type of JS interop function. Only external, primitive, string, and function types are supported in Kotlin/Wasm JS interop.. Tried also with Number as the arg type. Is there an idiomatic way of dealing with these? Maybe even the function's body can be implemented in a better way, but first I need to sort out the function's signature being invalid

[Robert Jaros]

You can only use JsAny.

[Piotr Krzemiński]

but it's not available in the common source set, in the expect function

[Robert Jaros]

You could create a second, private function with JsAny parameter and call it with some forced, unsafe casting. But it will crash is you pass something other than js object.

[Piotr Krzemiński]

sorry, I don't quite get how I would get past having a valid arg type in actual function for Wasm

[Robert Jaros]

https://pl.kotl.in/TZ-LJReKg

[Piotr Krzemiński]

fun isInteger(value: Any) works fine, what's problematic is *actual* fun isInteger(value: ???)

[Piotr Krzemiński]

wait a minute, there's something wrong on my side, one sec

[Robert Jaros]

the first function in my example can be your "actual"

[Robert Jaros]

it's just a simple function and can have Any parameter

[Robert Jaros]

the second is JS interop and must have JsAny

[Robert Jaros]

you can call the second by casting Any to JsAny, but as you can see it doesn't work as you could expect (calling with 5 returns false).

[Robert Jaros]

also no need for return in js()

[Piotr Krzemiński]

hmm, right - works in regular JS, doesn't work in JS interop, interesting

[Piotr Krzemiński]

tried with:

private fun isIntegerPrv(value: JsAny): Boolean = js("Number.isInteger(new Number(value))")

but got

Unhandled JavaScript exception: can't convert value to number

[Robert Jaros]

https://pl.kotl.in/ShjFkqWKH
check what is logged to the browser console

[Robert Jaros]

when you pass 5.toJsNumber() you get 5, when you pass 5 you get WasmStructObject

[Piotr Krzemiński]

good stuff, thanks! I need to make it work also for other number types, but I'll try to get it from here

[Robert Jaros]

(at least it doesn't crash anymore - I'm sure something like that crashed not long ago 😉 - but I can be wrong because my example works the same with 1.9 as well 😉)

[CLOVIS]

You could create a second, private function with JsAny parameter and call it with some forced, unsafe casting.

At this point, that second function could just be dynamic

[CLOVIS]

Ah no sorry this is #CDFP59223, not #C0B8L3U69 🙏

[turansky]

@file:JsQualifier("Number")

internal external actual fun isInteger(value: JsAny): Boolean

😉

[turansky]

And isInteger from Kotlin Wrappers can be used

[Piotr Krzemiński]

looks like reflection works pretty well for WASM - I was able to reuse the approach I have for the JVM:

fun isInteger(value: Number): Boolean {
    return value is Byte || value is Short || value is Int || value is Long
}

demo