This script work perfectly on procedural, but in ci4, 'keyup' function doesn't work 🤔

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.6.0/jquery.min.js"></script>
<script>
$(document).ready(function() {
  $("#search").keyup(function() {
    $.ajax({
      url: 'backend.php',
      type: 'post',
      data: {search: $(this).val()},
      success: function(result) {
        $("#result").html(result);
      }
    });
  });
});
</script>

Is there somebody would like to help me please.. 😫