The currently focused thread or stack frame, or undefined if no
thread or stack is focused. A thread can be focused any time there is
an active debug session, while a stack frame can only be focused when
a session is paused and the call stack has been retrieved.
The currently focused thread or stack frame, or
undefinedif no thread or stack is focused. A thread can be focused any time there is an active debug session, while a stack frame can only be focused when a session is paused and the call stack has been retrieved.