Comment by Too

I don't know if that's idiomatic webcomponent or not but that looks unmaintainable, even for such a minimal component, imagine once it grows. It's not separating presentation from state and logic. querySelector need to match classes and elements in the markdown. Mutating textContent is going to run out of sync as soon as you have more than one event source doing the same. Those are all problems that React solve by separating state and only rendering in one path.