javascript check if file exists in a loop of table rows

gistfile1.txt

            $(selector).on('click', '#id or .class name',  function() {
                
                var id = $(this).closest('tr').find('#id').val();
                //post the id to a url to update
                $.post('/url', {
                   id: id
                });
            });

            setInterval(function () { update() }, 10000);

            function update() {
                $('.loader').each(function () {
                    var id = $(this).closest('tr').find('#id').val();
                    var response = $.ajax({
                        url: '/tmp/file_name_' + id + '.pdf',
                        type: 'HEAD',
                        async: false
                    }).status;
      
                    if (response == 404) {
                        $(this).html("<i class='btn btn-primary fa fa-refresh print'>");
                    } else {
                        $(this).html("<i class='btn btn-danger fa fa-print'></i>")
                    }
                });
            }