Counting cells with a specific class in JavaScript

I have a HTML table and the following script to add a specific class to the cells, depending on their content.

Now, I would like to count only the items with class = active and trigger a modal (autoOpen: true) with the number of those items.
Any suggestions?

<script>
$('td').each(function() {
var $this = $(this)
  if ($this.text().match(new RegExp(/^[0-9][A-Z]/)) !== null ) {
    $this.addClass('active');
  }
  if ($this.text().match(new RegExp(/^c[0-9]/)) !== null ) {
    $this.addClass('none');
  }
});
</script>