I'm disappointed that the (formerly?) built-in Scala XML handling could not be used for JSX vs these:

Slinky:

   div(
      h3("TODO"),
      TodoList(items = state.items),
      form(onSubmit := (handleSubmit(_)))(
        input(
          onChange := (handleChange(_)),
          value := state.text
        ),
        button(s"Add #${state.items.size + 1}")
      )
    )

scalajs-react:

    <.div(
      NoArgs(),
      Hello("John"),
      Hello("Jane"))