handleChildClick = async function (event) {
      await deleteAllListeners(PARENT);
    }
The entire event registration state of the world should be "locked-in" at
the time the event occurs. This is to resolve many edge cases that come
about from a listener on a lower-in-DOM node causing structural changes at
places higher in the DOM. If this lower-in-DOM node causes new content to
be rendered at a place higher-in-DOM, we need to be careful not to invoke
these new listeners.