GetScrolledPos

function getScrollPosition() {
  var last_known_scroll_position = 0;
  var ticking = false;
  var bodyEl = document.body;
  var htmlEl = document.documentElement;
	var height = Math.max(bodyEl.scrollHeight, bodyEl.offsetHeight, 
                     		htmlEl.clientHeight, htmlEl.scrollHeight, htmlEl.offsetHeight);
  
  window.addEventListener('scroll', function(e) {
    last_known_scroll_position = window.scrollY;
    if (!ticking) {
      window.requestAnimationFrame(function() {
        onScroll(last_known_scroll_position);
        ticking = false;
      });
    }
    ticking = true;
  });

  function onScroll(yPos) {
    console.log(yPos);
    console.log(height);
    console.log((yPos / height) * 100);
  }
};

getScrollPosition();