JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.15.1/moment.js"></script>
<input type="button" value="Check Date"  class="validateDate"/>

JavaScript

$(function(){
  var dateFormat = 'YYYY-MM-DD';
  $('.validateDate').click(function(){
      alert(moment(moment("12/__/____").format(dateFormat),dateFormat,true).isValid());
  });
});