PGR - Validation before clicking next button

Thats possible only using JS. 

I tried a couple AI recommended javascripts but wasn’t successful. 

!--scriptorstartfragment-->

Qualtrics.SurveyEngine.addOnload(function () {

  var $this = this;

  // Watch for any change in group selections

  jQuery('select.QPGRGroup').on('change', function () {

    var selectedGroup = jQuery(this).val();

    if (!selectedGroup) return;

    // Find other items assigned to the same group

    jQuery('select.QPGRGroup').not(this).each(function () {

      if (jQuery(this).val() === selectedGroup) {

        jQuery(this).val(''); // clear previous selection

      }

    });

  });

});
***!--scriptorendfragment-->

Above is the javascript i’m using but it’s not working. I can still add multiple choices to a single group. 

The code below should work. Change the QID as per your Question ID.

Code ---

Qualtrics.SurveyEngine.addOnReady(function () {

    var SOURCE_ID = "#QID72items";
    var GROUP_IDS = ["#QID72group0", "#QID72group1"];

    function enforceOneItemPerGroup(groupEl) {
        if (groupEl._pgr_observer) return;

        var observer = new MutationObserver(function (mutations) {
            var hasAddition = mutations.some(function (m) {
                return m.type === "childList" && m.addedNodes.length > 0;
            });

            if (!hasAddition) return;

            // Target li items directly (excluding header/label rows)
            var items = jQuery(groupEl).find("li[role='listitem']");

            if (items.length > 1) {
                var oldItem = items.first();

                observer.disconnect();

                // Send old item back to the source list
                jQuery(SOURCE_ID).append(oldItem);

                setTimeout(function () {
                    observer.observe(groupEl, { childList: true, subtree: true });
                }, 100);
            }
        });

        observer.observe(groupEl, { childList: true, subtree: true });
        groupEl._pgr_observer = observer;
    }

    function init() {
        GROUP_IDS.forEach(function (selector) {
            var el = document.querySelector(selector);
            if (el) {
                enforceOneItemPerGroup(el);
            } else {
                var retries = 0;
                var interval = setInterval(function () {
                    var el = document.querySelector(selector);
                    if (el) {
                        enforceOneItemPerGroup(el);
                        clearInterval(interval);
                    }
                    if (++retries > 20) clearInterval(interval);
                }, 100);
            }
        });
    }

    init();
});