code: function offset(el) {
    const rect = el.getBoundingClientRect();
    const scrollTop = window.pageYOffset || document.documentElement.scrollTop || document.body.scrollTop || 0;
    const scrollLeft = window.pageXOffset || document.documentElement.scrollLeft || document.body.scrollLeft || 0;
  
    return {
      top: rect.top + scrollTop,
      left: rect.left + scrollLeft
    };
  }
docs: IE8+ equiv. of $.fn.offset