Pop-Up Window, Center Screen

Question

I\'m using the following code to open a pop-up window in a Google Chrome extension, my one question is, how do I get the pop-up window to open in the centre of the users screen?

Answer 1

As an addendum to this answer, if you want to retrieve popup dimensions from localstorage--which are saved as strings--this will convert the variables to the necessary integers for the pop-up to work.

 var w =  parseInt(localStorage.getItem('key'));
 var h =  parseInt(localStorage.getItem('key'));