In the no-paste link I found the following:
window.open('localhost:8000/player/index.html','MyWindow','toolbar=no,location=no,directories=no,status=no, menubar=no,scrollbars=no,resizable=no,width=600,height=300')
It should work if you add the protocol to the url like so:
window.open('http://localhost:8000/player/index.html','MyWindow','toolbar=no,location=no,directories=no,status=no,menubar=no,scrollbars=no,resizable=no,width=600,height=300')
That way, the browser knows it's an absolute Url.