Sticky sidebar

I found this code here https://andrewhenderson.me/tutorial/jquery-sticky-sidebar/ and wanted to try it. Unfortunately I can’t make it work.

I understand my div must be renamed to .sticky, but I believe there is something with the jQuery that I don’t understand.

Here’s my code I use in functions.php:

wp_enqueue_script("jQuery");
$(function(){ // document ready

  if (!!$('.sticky').offset()) { // make sure ".sticky" element exists

    var stickyTop = $('.sticky').offset().top; // returns number 

    $(window).scroll(function(){ // scroll event

      var windowTop = $(window).scrollTop(); // returns number 

      if (stickyTop < windowTop){
        $('.sticky').css({ position: 'fixed', top: 0 });
      }
      else {
        $('.sticky').css('position','static');
      }

    });

  }

});

Help very much appreciated
/Ca