JavaScript: Restrict with only one window popup

Hello Folks,

I've a website & with an option to open window popup.
I am able to open window popup & restricted with same popup (in case user click again to open window popup) but once request post then again, new popup opens (if user clicks on that option).

FYI, used

var newWindowpopup = null

checked for equal to null OR closed then open new window otherwise not

Select allOpen in new window

Do you have any thought to open same window popup (if already open) irrespective post to server? As you know, it should be browser compatibility.

Best Regards