relatedTarget property

EventTarget? get relatedTarget

The MouseEvent.relatedTarget read-only property is the secondary target for the mouse event, if there is one.

That is:

Event name	target	relatedTarget
[Element.mouseenter_event]	The [EventTarget] the pointing device entered to	The [EventTarget] the pointing device exited from
[Element.mouseleave_event]	The [EventTarget] the pointing device exited from	The [EventTarget] the pointing device entered to
[Element.mouseout_event]	The [EventTarget] the pointing device exited from	The [EventTarget] the pointing device entered to
[Element.mouseover_event]	The [EventTarget] the pointing device entered to	The [EventTarget] the pointing device exited from
[HTMLElement.dragenter_event]	The [EventTarget] the pointing device entered to	The [EventTarget] the pointing device exited from
[HTMLElement.dragleave_event]	The [EventTarget] the pointing device exited from	The [EventTarget] the pointing device entered to

For events with no secondary target, relatedTarget returns null.

FocusEvent.relatedTarget is a similar property for focus events.

Implementation

external EventTarget? get relatedTarget;