relatedTarget property

EventTarget? get relatedTarget

The relatedTarget read-only property of the FocusEvent interface is the secondary target, depending on the type of event:

Event name	target	relatedTarget
[Element.blur_event]	The [EventTarget] losing focus	The [EventTarget] receiving focus (if any).
[Element.focus_event]	The [EventTarget] receiving focus	The [EventTarget] losing focus (if any)
[Element.focusin_event]	The [EventTarget] receiving focus	The [EventTarget] losing focus (if any)
[Element.focusout_event]	The [EventTarget] losing focus	The [EventTarget] receiving focus (if any)

Note that many elements can't have focus, which is a common reason for relatedTarget to be null. relatedTarget may also be set to null for security reasons, like when tabbing in or out of a page.

MouseEvent.relatedTarget is a similar property for mouse events.

Implementation

external EventTarget? get relatedTarget;