interoperable.md

```kotlin // Use any existing JVM library or framework // Call Kotlin code from Java without an issue

@SpringBootApplication class DemoApplication

fun main(args: Array) { runApplication(*args) }

@RestController class MessageResource { @GetMapping fun index(): List = listOf( Message("1", "Hello!"), Message("2", "Bonjour!"), Message("3", "Privet!"), ) }

data class Message(val id: String?, val text: String)

</div>

<div class="sample" markdown="1" mode="kotlin" theme="kotlin-docs" data-highlight-only="1" auto-indent="false">

// Write Kotlin code, compile it to JavaScript, and run it in the browser // Use existing JavaScript APIs and libraries

import kotlinx.browser.window

fun main() { val body = window.document.body

body?.innerHTML += "Hello, Kotlin"

window.setInterval({ body?.innerHTML += "!" }, 1000) }

</div>

<div class="sample" markdown="1" mode="kotlin" theme="kotlin-docs" data-highlight-only="1" auto-indent="false">
```kotlin
// Use Kotlin wrappers to build applications with JavaScript frameworks such as React

import react.*
import react.dom.*
import kotlinx.html.js.onClickFunction

val counter = functionalComponent<Props> {
   val (count, setCount) = useState(0)
   button {
      attrs.onClickFunction = { setCount(count + 1) }
      +count.toString()
   }
}