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];
  }
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