JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://code.jquery.com/jquery-2.2.3.min.js"></script>
<input type="button" onclick="createCheck()" value="create" />
<input type="button" onclick="reset()" value="Reset" />

<input type="button" onclick="countChecked()" value="Count Checked" />

JavaScript

function createCheck() {
  $('body').append('<input type="checkbox" name="is_chosen[]" value="1" class="flat dynmc-check">');
}

function reset() {
  $('.dynmc-check').removeAttr('checked');
}

function countChecked() {
  var checkCount = $('.dynmc-check:checked').length;
  console.log(checkCount);
}