Gegam

var scrollDepthtracking = {}
var contentMaxHeight = Math.max( document.body.scrollHeight, document.body.offsetHeight, 
                   document.documentElement.clientHeight, document.documentElement.scrollHeight, document.documentElement.offsetHeight)

window.addEventListener('scroll', function () {
  
  var currentPos = document.body.scrollTop || window.pageYOffset || document.documentElement.scrollTop
      , documentHeight = document.body.offsetHeight
      , windowHeight = window.innerHeight
      , scrollPercent = Math.ceil((currentPos + 5) / (contentMaxHeight * 10) * 10