This function doesn't change the request response message, but instead throws a custom message. The use of this with request/force response in not recommended.
Qualtrics.SurveyEngine.addOnReady(function () {
const qid = this.questionId;
tot_choices = Qualtrics.SurveyEngine.registry[qid].getChoices().length;
var sel_choices = 0;
that = this;
this.questionclick = function () {
sel_choices = that.getSelectedChoices().length;
};
document.querySelector("#NextButton").onmousedown = function () {
check_answers();
};
function check_answers() {
if (sel_choices == tot_choices) {
that.clickNextButton();
} else {
//Selecting Okay will result in continuing
if (confirm("Custom message here") == true) {
that.clickNextButton();
}
}
}
});