how can the children listen/capture to the parent's event

Question

how can the parent fire the custom event to notify its children/siblings? for example:

Answer 1

customEvent2 is only bound to div2. When you try to trigger it on div1, nothing happens because that event doesn't exist for div1.

If you want to fire customEvent2, it has to be triggered on an element (or child of one) it is actually bound to.