Execute some JS to register the action in Google Analytics

I want to execute some JS to register the action in Google Analytics after a form is submitted. The form is made in MailChimp and is using ajaxSuccess. But the script runs on page load instead form submission.

The ajax function that submits the form is in the plugin that is hosted on github (https://github.com/ibericode/mailchimp-top-bar/blob/master/assets/js/script.js). You can see the code on Line #229

Can someone assist in fixing this?