title: How to call root parent's function from n-th child window using javascript?
body: <p>there.
  Let's say that I don't know how many child window would be open by window.showModalDialog.
  If it's only 1 depth between child and parent, it would be easy to call parent's function using javascript.
  But I have to open a child window and from that child window to another child window, and another, and another.
  I can't say how many depth.
  Now, from the last child window, how can I call the root parent's function?
  Anyone has any idea?</p>
  
  <p>"Root Parent Window" -> child window -> child window -> child window ........n-th child window</p>