JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.16/themes/base/jquery-ui.css">
<div class="eventsRowsWrapper">
  <div class="eventsRows sortable">
    <div class="form-group multi-event controls form-inline">
   
      <input name="date[]" maxlength="255" type="text" placeholder="Data" class="datepickerClass form-control sortable ui-sortable" size="20">

      <button type="button" style="float: none" class="close deleteEventButton">&times;</button>
    </div>
  </div>
  <button class="btn btn-warning btn-sharp addEventButton" type="button" name="addEvent"><span class="glyphicon glyphicon-plus-sign"></span>Add event</button>
</div>

JavaScript

$(document).ready(function() {

        $('.eventsRowsWrapper').each(function() {
            var $wrapper = $('.eventsRows', this);

            $(".addEventButton", $(this)).on('click', function() {
                //console.log(jsFrontend.data.get('Planning.test'));
                //$('.multi-event:first-child').clone(true).appendTo($wrapper).find('input').val('').attr('id', '');
                $($wrapper).append('<div class="form-group multi-event controls form-inline"> <input name="date[]" maxlength="255" type="text" placeholder="Data" class="datepickerClass form-control sortable ui-sortable" size="20"> <button type="button" style="float: none" class="close deleteEventButton">&times;</button></div>');
                $(".datepickerClass").datepicker();
                $('.sortable').sortable();
            });

            $('.multi-event').on('click', '.deleteEventButton', function() {
                    if ($('.multi-event', $wrapper).length > 1){
                    $(this).parent('.multi-event').remove();
                }
            });
        });

     });