JSFiddle - React, Tailwind, and code Playground

HTML

<section>
  <div class="container">
   <select id="myId_1" name="myName_1">
     <option value="1">1</option>
     <option value="2">2</option>
   </select>
  </div>
</section>
<button type="button" id="myBtn">add</button>

JavaScript

$(document).ready(function () {
    $('#myBtn').click(function(){
        var addEvent = $('.container:last').html();
      var addEventCell = $('<div class="container">'+addEvent+'</div>');
      var select = $('select', addEventCell);
        console.log(select);
      var oldId = select.attr('id');
      var newId = oldId.split('_')[0] + '_' + (parseInt(oldId.split('_')[1]) + 1);
      select.attr('id', newId).attr('name', newId);
      $('section').append(addEventCell);
    });
  });