Why does the FadeIn/Out function not work when moving from JQuery 2.2.4 to 3.6.0

Question

I have a loader that is shown until the page is done loading that then fades out while the page fades in. I put the code in the head of my website. I decided to move from JQuery 2.2.4 to 3.6.0 and now it's not working. What was changed between these two versions?
Here's the code:

<script>
  $(window).load(function() {
    $("#loader").fadeOut("slow");;
    $("#page").fadeIn("slow");;
  });
</script>