code: function scrollTop(...args) {
    let [top, duration, easing, callback] = args;
    if (args.length === 3 && typeof easing === 'function') {
      [top, duration, callback, easing] = args;
    }
    const dom = this;
    if (typeof top === 'undefined') {
      if (dom.length > 0) return dom[0].scrollTop;
      return null;
    }
    return dom.scrollTo(undefined, top, duration, easing, callback);
  }
docs: scrollTop(top, duration, easing, callback) {