Help in Custom JavaScript Display and Grading Problem

Development
1

I am trying to implement custom javascript problem. I have my javascript application.
But when I submit my problem it shows “Could not grade your answer. The submission was aborted.”
Here code
`
let func = (function() {
function showQue() {
let checkBox = document.getElementById(“checkBox”);
let text = document.getElementById(“question”);
if (checkBox.checked == true){
text.style.display = “block”;
} else {
text.style.display = “none”;
}
}

      function getGrade() {
          return "correct"
      }

      return {
          showQue: showQue,
          getGrade: getGrade
      }
    })();
</script>
`

and the problem “cms-modules.2b7ffc378730.js:175 Uncaught TypeError: Cannot read property ‘getGrade’ of undefined”. Not sure what I am missing.