How do i get the parameters from .xml file to .js file?

I am developing a module for Joomla!
I dont want to set the size of the width and height as this (in the .js file)!
I want the administrator to be able to set width and height in the administrator parameters (the .xml file).
I'm stuck, can someone point me in the right direction?
How do i get the parameters from the .xml file to the .js file?

This is the .js file.

var newwindow;
function poptop(url)
{
   newwindow=window.open(url,'name','height=400,width=600,toolbar=no,location=no,status=no,menubar=no,scrollbars=no,resizable=no');
   if (window.focus) {newwindow.focus()}
}

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