title: Does the event `invalid` only fire once?
body: <p>I tried to hook into the <a href="https://developer.mozilla.org/en-US/docs/Web/API/HTMLInputElement/invalid_event" rel="nofollow noreferrer"><code>invalid</code></a> event for numeric input (which is required), and while the <code>invalid</code> event fires right on loading the page (as all the cells are empty), it does not refire if one fills an input field and removes its content or inputs a letter instead of a number. But I could not find anything indicating that this would be its behaviour. But at the same time I can also not find an issue with my code. So I guess I am first asking what the desired behaviour is before I continue hunting for bugs.</p>