Normally, JS event are handled while bubbling up the DOM tree, and we've all had the pleasure to catch an event from a child node on its parent. You'd even be excused for thinking that's the only way DOM events move. Many also know there's something else — events start at the document root, then go down to the affected element in a phase called "capture", and only then "bubble" back up (not all do — more on this in a minute). See MDN article on events for more details on this mechanism.
