we can add required field validation easily using jquery if we have textbox, textarea, select box etc, but if we used ckeditor then it's not simple. In this example i give you how to add Ckeditor required field validation in javascript. we can do it using CKEDITOR.instances, so if you also require then you can use it.
Example:
<html lang="en">
<head>
<title>Jquery - ckeditor required field validation</title>
<script type="text/javascript" src="//cdn.jsdelivr.net/jquery/1/jquery.min.js"></script>
<script src="//cdn.ckeditor.com/4.5.9/standard/ckeditor.js"></script>
</head>
<body>
<div class="container text-center">
<form>
<textarea name="editor"></textarea>
<button>Submit</button>
</form>
<script>
CKEDITOR.replace( 'editor' );
$("form").submit( function(e) {
var messageLength = CKEDITOR.instances['editor'].getData().replace(/<[^>]*>/gi, '').length;
if( !messageLength ) {
alert( 'Please enter a message' );
e.preventDefault();
}
});
</script>
</div>
</body>
</html>