The FocusEvent.relatedTarget read-only property is the secondary target, depending on the type of event:
| Event name | target | relatedTarget |
|---|---|---|
blur | The EventTarget losing focus | The EventTarget receiving focus (if any). |
focus | The EventTarget receiving focus | The EventTarget losing focus (if any) |
focusin | The EventTarget receiving focus | The EventTarget losing focus (if any) |
focusout | 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.