Getting Uncaught TypeError: Cannot read properties of undefined (reading 'then') while working with Javascript Promise

Question

I declare a window promise where I get a response and stor it in a JS ojbect. The script does not get executed. I am getting an error while working with the Javascript promise:

Cannot read properties of undefined (reading 'then')

window.promise.then(function(response) {
  var jsObject = JSON.parse(response);

  if (jsObject.enableEmailVerificationOnRegistration) {
    alert('hii enable verification tggle is on')
    var signUpClick = document.getElementById("registrationSignUp");
    signUpClick.addEventListener('click', function(e) {
      event.preventDefault();
      var getPdpUrl = window.parent.location.pathname;
      document.getElementById("pdpUrlValue").value = getPdpUrl;
      localStorage.setItem("currentPdpPath", getPdpUrl);
      window.location.href = getPdpUrl;
    });
  }
});