gem datepicker formate jquery

_form.html.erb

<script type="text/javascript">
  $(document).ready(function(){
    $(".datepicker").datepicker({
        dateFormat: 'dd-mm-yy' 
    })
    .on("changeDate", function (e) {
      var start_date = $("#txtStartDate").val();
      var end_date = $("#txtEndDate").val(); 
      if (start_date != "" && end_date != ""){
        start_date = new Date(start_date);
        end_date = new Date(end_date);
        if (end_date < start_date){
          alert("End date should be greater or equal to start Date");
          $(this).val("");
        }
      }
    });
  });
</script>