How do I automate loading all of a browser page that is dynamically loaded?

Question

I am trying to automate paging to the true bottom of a web page which is dynamically loaded; that is, a page which takes multiple page-downs or Ctrl-Ends to get to the real bottom (e.g., Netflix). I've got the basics done:

var timerID = setInterval(scrollDown,1000); 
function scrollDown() { 
  window.scrollTo(0, document.body.scrollHeight); 
  if ((window.innerHeight + window.scrollY) >= document.body.scrollHeight)  { 
    clearInterval(timerID); 
    alert("End of Page");
  }
}

(I compact all of the above onto one line preceded by "javascript:" and make it a bookmark.) There have been numerous suggestions here on the correct comparison for the "if" statement, but as far as I know, none of them take into account dynamic loading. My thought was to capture the current bottom line number or location and compare it in the "if" statement to the immediately previous value, and if they are the same, assume you really are at the bottom. I don't know how to capture the current bottom line info, but I would also be open to alternative approaches. Thank you.

Fred