the process by which the browser decides which objects to trigger on.
3 phases of event propagation:
(“capturing” phase) occurs before the target handlers are invoked.
(“bubbling” phase) event bubbling.
most events to the object, and then to the object, notable exceptions are the “focus” “blur,” and “scroll” events.
a can stop the event from bubbling by calling .
The capturing phase is like the bubbling phase in reverse.
capturing handlers of the object are invoked first.
then the capturing handlers of the object, and so on.
event target's capturing handlers are NOT invoked.
