If I want to access an external javascript variabl...

# javascript

[Jonathan Ellis]

If I want to access an external javascript variable from my code, is js("foo") as Type the best option? What about going the other way around, do I need to generate js("foo = [js string representation]")? This is easy for primitives but more tedious for other objects

[ephemient]

external var foo: Type

[Jonathan Ellis]

ah, thanks. wasn't sure from docs if that would work

[Jonathan Ellis]

I can't figure out how to get this to work with a map

[Jonathan Ellis]

<script>
        let foo = 0.0
        let bar = {}
    </script>

[Jonathan Ellis]

external var foo: Double
external var bar: MutableMap<String, Any>

[Jonathan Ellis]

foo = 1.0
bar["test"] = "a"

[Jonathan Ellis]

foo works as expected

[Jonathan Ellis]

bar says

[Jonathan Ellis]

Uncaught TypeError: tmp0_set_0.put_3mhbri_k$ is not a function

[ephemient]

MutableMap is a Kotlin type, but {} in JS is not

[ephemient]

external val bar: dynamic
bar["test"] = "a"

[Jonathan Ellis]

wow, black magic 🙂 that works

[Big Chungus]

external val bar: Json

It's safer and represents js object types

[Jonathan Ellis]

perfect, thanks

[ephemient]

dynamic lets you write bar.test = "a" just like you can in JS, which you could consider a plus and/or a minus

[Jonathan Ellis]

that makes sense

[Big Chungus]

Dynamic type is basically an escape hatch to tell the compiler to completely drop the type safety. It's necessary to handle some janky js voodoo interop, but in general should be avoided as much as possible (otherwise you're better off to just coding in plain js)

[Big Chungus]

Not sure if you've seen it yet, but I've written an article that covers most of what one needs to know when interoping with js
https://dev.to/mpetuska/js-in-kotlinjs-c4g

[Jonathan Ellis]

Reading now. Thanks!