Get the current response onSubmit

This code gives you the values for the last form response, is that what you're looking for ?

function myFunction() {
  var formResponses = FormApp.getActiveForm().getResponses();
  Logger.log(formResponses.length);
  var formResponse = formResponses[formResponses.length-1];
  var itemResponses = formResponse.getItemResponses();
  for (var j = 0; j < itemResponses.length; j++) {
    var itemResponse = itemResponses[j];
    Logger.log('Last response to the question "%s" was "%s"',
               itemResponse.getItem().getTitle(),
               itemResponse.getResponse());
  }
}