Property updated hook in Javascript

Is there a way to listen to updated properties from Javascript without having to emit a separate event?
Basically instead of doing public function updatedWhatever in php, something like window.livewire.on('updatedWhatever') that works out of the box.

If your sticking to javascript, you probably don’t need livewire to do anything, so why not just use javascript’s onChange, onInput, onKeydown etc?