Ghost subscription tracker

on-subscribe.js

if ("MutationObserver" in window) {
    var observer = new MutationObserver(function(mutations) {
        mutations.forEach(function(mutation) {
          var form = mutation.target;
          if (form.classList.contains('success') && mutation.oldValue != '') {
            // TRACK HERE
          }
        });
     });

    var subscriptionForms = document.querySelectorAll('form[data-members-form="subscribe"]');

    subscriptionForms.forEach(function (form) {
      observer.observe(form, { 
        attributes: true,
        attributeOldValue: true,
        attributeFilter: ['class'] 
      });
    });
}