composed property
The read-only composed property of the
Event interface returns a boolean value which indicates whether
or not the event will propagate across the shadow DOM boundary into the
standard DOM.
All UA-dispatched UI events are composed
(click/touch/mouseover/copy/paste, etc.). Most
other types of events are not composed, and so will return false. For
example, this includes synthetic events that are created without their
composed option set to true.
Propagation only occurs if the Event.bubbles property is also
true. However, capturing only composed events are also handled at host
as
if they were in AT_TARGET phase. You can determine the path the event
will
follow through the shadow root to the DOM root by calling
Event.composedPath.
Implementation
external bool get composed;