code: function getScroll(element) {
    var side = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : 'top';
  
    var upperSide = side === 'top' ? 'scrollTop' : 'scrollLeft';
    var nodeName = element.nodeName;
  
    if (nodeName === 'BODY' || nodeName === 'HTML') {
      var html = element.ownerDocument.documentElement;
      var scrollingElement = element.ownerDocument.scrollingElement || html;
      return scrollingElement[upperSide];
    }
  
    return element[upperSide];
  }
docs: Gets the scroll value of the given element in the given side (top and left)
  @method
  @memberof Popper.Utils
  @argument {Element} element
  @argument {String} side `top` or `left`
  @returns {number} amount of scrolled pixels