title: How do I make my navbar change CSS class upon scrolling past an anchor point?
body: <p>I'm using Bootstrap 3 and want to achieve <a href="http://whiteboard.is/" rel="noreferrer">this effect</a> when the user scrolls past the large header image on my page. I need the background of the navbar to go from transparent to white. I looked in their code and I KNOW it is done with javascript, and even saw <a href="http://wb4.s3.amazonaws.com/wp-content/themes/wb4/js/main.min.js.gzip" rel="noreferrer">WHERE</a> it was happening I think (look for the ID '#main-header' in that JS)... </p>
  
  <p>Not knowing advanced Javascript aside, I'm looking for a way to apply this to my navigation bar when scrolling past a certain point. The class for my code is called 'navbar' and I would like it to turn white when it passes "#main". Let me know if you need more information, and thanks in advance if anyone wants to help!</p>