How to tell if window.open created new?

[kj]

Suppose I have the line

w = window.open("", "foobar");

How can I tell whether this call to window.open created a new window
or simply returned a pointer to an already existing window called
"foobar"?

Thanks!

kj
--
NOTE: In my address everything before the first period is backwards;
and the last period, and everything after it, should be discarded.

[Richard Cornford]

kj wrote:

Suppose I have the line

w = window.open("", "foobar");

How can I tell whether this call to window.open created a new
window or simply returned a pointer to an already existing
window called "foobar"?

There would be no difference to detect much of the time. If an already
open window has been in use it may have acquired length to its history,
but that is not guaranteed to have happened.

Richard.