title: How to detect if browser window is scrolled to bottom?
body: <p>I need to detect if a user is scrolled to the bottom of a page. If they are at the bottom of the page, when I add new content to the bottom, I will automatically scroll them to the new bottom. If they are not at the bottom, they are reading previous content higher on the page, so I don't want to auto-scroll them since they want to stay where they are.</p>
  
  <p>How can I detect if a user is scrolled to the bottom of the page or if they have scrolled higher on the page?</p>