JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/ckeditor/4.2/ckeditor.js"></script>

<form><textarea id=foo></textarea></form>
<button id="validar">Validar</button>

JavaScript

CKEDITOR.replace('foo');

document.getElementById('validar').addEventListener('click', function(){
	if (/^\s*$/.test(CKEDITOR.instances.foo.document.getBody().getText())) {
  	alert('VacĂ­o');
  } else {
  	alert('Cosas');
  }
});