Hello! I've found a little bug with callback mechanism.
In my app i'm relying on window.addEventListener('scroll', /** my super code **/ ).
I also relying on jumper's callback option, and sometimes callback executes before the last scroll event happens.
See: https://jsfiddle.net/mxqfjLge/ (I hope it will reproduce on your screen resolution)

i have prepared PR #56 to fix this