Hide element on scroll

gistfile1.js

(function(document, window) {
  
  var element = document.getElementById('hide-scroll');
  var elementHeight = element.clientHeight;
  var elementTop = praseInt(element.style.top, 10) || 0;
  var distance = elementTop;
  
  /**
   * Get delta from 'mousewheel'
   * @param  {Object} e event object
   * @return {Array}   returns array with delta
   *
   * @source: https://github.com/noraesae/perfect-scrollbar/blob/master/src/js/plugin/handler/mouse-wheel.js
   */
  function getDeltaFromEvent(e) {
        var deltaX = e.deltaX;
        var deltaY = -1 * e.deltaY;

        if (typeof deltaX === 'undefined' || typeof deltaY === 'undefined') {
          // OS X Safari
          deltaX = -1 * e.wheelDeltaX / 6;
          deltaY = e.wheelDeltaY / 6;
        }

        if (e.deltaMode && e.deltaMode === 1) {
          // Firefox in deltaMode 1: Line scrolling
          deltaX *= 10;
          deltaY *= 10;
        }

        if (deltaX !== deltaX && deltaY !== deltaY /* NaN checks */ ) {
          // IE in some mouse drivers
          deltaX = 0;
          deltaY = e.wheelDelta;
        }

        return [deltaX, deltaY];
      }
  
  /**
   * Hide element on scroll
   * @param {Object} event gets event object
   * 
   */
  function hideOnScroll(event) {
    var deltaY = getDeltaFromEvent(event.originalEvent)[1] / 2;
    
    distance += deltaY;

    if (distance > -elementHeight && distance < 0) {
      $el.css('top', Math.floor(distance));
    } else {
      distance = parseInt($el[0].style.top, 10);
    }
    
  }
  
  window.addEventListener('mousewheel', hideOnScroll);
  window.addEventListener('DOMMouseScroll', hideOnScroll);
  
}(document, window));