And I have no idea how does it work :slightly_smiling_face: I've just added `external interface Wind...

# webassembly

[Robert Jaros]

And I have no idea how does it work 🙂 I've just added external interface Window with alert() method, external val window : Window and I've got window.alert() working. How does it talk to the browser API?? Is it documented somewhere what is possible (what should be possible)?

[ESchouten]

Perhaps we could generate the interfaces? Perhaps with help from Dukat?

[jessel]

The wasm compiler generates a small binding layer with javascript which automatically exposes the wasm code to the javascript world and vice versa based on your external statements

[Robert Jaros]

How can I expose kotlin code (e.g. some data class or function) to JS?

[Robert Jaros]

If I pass kotlin data class to JS function I receive empty object {} on JS side.

[Robert Jaros]

I can pass JS classes without problems

[Svyatoslav Kuzmich [JB]]

external s work for the most part similar to K/JS. You cannot inherit or implement them. Design is not finished and we don’t have docs yet, but you can look at working examples at https://github.com/JetBrains/kotlin/tree/03c352c11e1ed0ca28653937c5f944883c5376b0/compiler/testData/codegen/boxWasmJsInterop

[Svyatoslav Kuzmich [JB]]

They work using externref Wasm types. Compiler generates needed function imports from JS.

[Svyatoslav Kuzmich [JB]]

How can I expose kotlin code (e.g. some data class or function) to JS?

You cannot at the moment. You can @JsExport top-level functions and use K/Wasm references as opaque objects.

[Robert Jaros]

Will dynamic be available in Kotlin/Wasm?

[Svyatoslav Kuzmich [JB]]

This is an open question. We need some type for accessing JS values dynamically but it would probably have more limitations compared to K/JS dynamic

[Svyatoslav Kuzmich [JB]]

We are prototyping dynamic-like type, but it is not merged yet, and this is not the final design