Script to correctly handle clicks on optional groups. An optional group needs to have a value in 'linkKey' no matter what. Salsa does not do this correctly and sometimes the wrong optional group is recorded. This script assures campaign managers that a clicked optional group either contains the groups_KEY or a zero.

optional_group_click_handler.html

<script type="text/javascript">
// Script to handle clicks on optional groups.
function optionalClick(event) {
  var elem = event.target;
  elem.value = elem.checked ? elem.getAttribute('alt-value') : 0;
}
// Find and configure all optional groups.
document.addEventListener("DOMContentLoaded", function() {
  Array.from(document.querySelectorAll('input[id^="add_to_groups_KEY"]')).forEach(function(e) {
    e.setAttribute('alt-value', e.getAttribute('value'));
    e.addEventListener('change', optionalClick);
  });
});
</script>