Any element that is an ancestor of the waypoint element.
This results in…
As you can see, this waypoint handler is triggered when the top of the element hits the top of its context element. The default of
window covers the most common case, the user is scrolling the window and we want to react to an element's position in relation to the top of the window.
The other part of this equation, where the waypoint triggers, can be controlled with the offset option. As with the default of
window, this offset is calculated in relation to the context. For example, an offset of
'50%' will trigger when the top of the element hits the midpoint in the context's height.
If you're using the jQuery or Zepto builds of Waypoints, you can pass a CSS selector string as the
context option, instead of an HTMLElement, and Waypoints will call closest to find the context element.