How does .waypoint work?

If a have a code like this

        var waypoint = new Waypoint({
element:document.getElementsByClassName  ('waypoint'),
 handler: function(direction) {
 console.log('Scrolled to waypoint!')
  }
})

And I have 10 elements that have 'waypoint' class,how does waypoint plugin control if those elements are visible in viewport?Does it control all div's offsets every time onscroll event is triggered?