CODE EXAMPLE FOR JAVASCRIPT

Appearing datepicker behind the modal

$('#dispatch_modal').on('shown.bs.modal', function() {
     $('input:text:visible:first').focus();
     // prepare datepicker
     $('.form_datepicker').daterangepicker({
          singleDatePicker: true,
          showDropdowns: true,
          parentEl: '#dispatch_modal'   
     });
});