Javascript to check for duplicate answers across 3 questions

Hey @Elisabeth 

if you want it like this

 You can use this code:

Qualtrics.SurveyEngine.addOnload(function() {

    var qid1 = "QID1";

    var qid2 = "QID2";

    var qid3 = "QID3";

    function getSelectedValue(qid) {

        var qContainer = document.getElementById(qid);

        var selectedInput = qContainer.querySelector("input[type='radio']:checked");

        return selectedInput ? selectedInput.value : "";

    }

    function checkForDuplicates() {

        var val1 = getSelectedValue(qid1);

        var val2 = getSelectedValue(qid2);

        var val3 = getSelectedValue(qid3);

        var values = [val1, val2, val3].filter(Boolean);

        var uniqueValues = new Set(values);

        return uniqueValues.size !== values.length;

    }

    function displayError(show) {

        var errorContainer = document.getElementById("customError");

        if (!errorContainer) {

            errorContainer = document.createElement("div");

            errorContainer.id = "customError";

            errorContainer.style.color = "red";

            errorContainer.style.fontWeight = "bold";

            errorContainer.innerText = "You have selected the same response in multiple questions. Please choose different responses.";

            document.getElementById("Questions").prepend(errorContainer);

        }

        errorContainer.style.display = show ? "block" : "none";

    }

    function validateDuplicates() {

        if (checkForDuplicates()) {

            displayError(true);

            document.querySelector("#NextButton").disabled = true;

        } else {

            displayError(false);

            document.querySelector("#NextButton").disabled = false;

        }

    }

    [qid1, qid2, qid3].forEach(function(qid) {

        var qContainer = document.getElementById(qid);

        var inputs = qContainer.querySelectorAll("input[type='radio']");

        inputs.forEach(function(input) {

            input.addEventListener("change", validateDuplicates);

        });

    });

    // Initial validation

    validateDuplicates();

});
 

make sure the Question ID “QID1, QID2 and QID3” are correct.

You write this code on the first question off the 3

Hi @RickB, that’s exactly what I’m after, thanks! I’ve added it in but can’t get it to work. I am using a select box and not a multiple choice question format so could that be the issue?