Create a Kotlin/JS WebComponent with content

I want to create a custom tag with Kotlin that contains default content. The linked example works fine, but I didn’t manage to add some default content (e.g. input element) to the custom tag.

I’ve tried different things, but so far only managed to add the input element next to the custom tag in the DOM, but not inside it.


<!DOCTYPE html>
<html lang="en">
    <meta charset="UTF-8">
    <title>JS Client</title>
<script src="webcomponentexampleproject.js"></script>
<div id="root"></div>


import kotlinx.browser.document
import kotlinx.browser.window
import kotlinx.html.InputType
import kotlinx.html.dom.append
import kotlinx.html.dom.create

fun main() {
    window.onload = {

        document.getElementById("root")!!.append {
            webcomponent {
                text = "added it"
                +"some more text"



import kotlinx.html.*
import kotlinx.html.js.onChangeFunction
import org.w3c.dom.HTMLInputElement

class WebComponent(consumer: TagConsumer<*>, _text: String = "", _backgroundColor: String = "none") :
    HTMLTag("webcomponent", consumer, emptyMap(), inlineTag = true, emptyTag = false), HtmlInlineTag {

    var text: String by Delegates.observable(_text) { prop, old, new ->
        el.value = text
    var backgroundColor: String by Delegates.observable(_backgroundColor) { prop, old, new -> = backgroundColor

    private val el: HTMLInputElement

    init {
        //TODO: this input element should be INSIDE the tag
        el = consumer.input {
            type = InputType.text
            value = this@WebComponent.text

// make the new custom tag usable via the kotlinx.html DSL
fun <T> TagConsumer<T>.webcomponent(block: WebComponent.() -> Unit = {}): T {
    return WebComponent(this).visitAndFinalize(this, block)