How to check CKEditor textarea not empty

<div class="ckarea" style="display:none;">Please enter Description</div>

<textarea name="longdesc" id="longdesc"></textarea>
<script>
CKEDITOR.replace( 'longdesc' );
</script>

<script>
$("form").submit(function(e) {
    var description = CKEDITOR.instances['longdesc'].getData().replace(/<[^>]*>/gi, '').length;
    if (!description) {
        $(".ckarea").show();
        return false;
    }
});
</script>