title: How to add a class to an element when enters view
body: <p>I am looking to add a class to a div when i scroll to the top of it and it comes just into view on the screen. 
  I have been able to do this when the whole height of the div is in view but not as i scroll and hit the top of it, perhaps with an offset ability?
  Very new to this so any help would be massively appreciated :)</p>