You can refer to code in Getting Value of Subform 

                my_name = $("#field2_subform_name"); //Get subform value

You will need to add prefix of your subform ID and subform form name when calling.

My Friend Bastiana , I found the problem in the original code that come with the demo application .

The code lack of this part in bold

<script type="text/javascript">
    $(document).ready(function(){
        selectmain = $(FormUtil.getField("field1")); //Get ID of subform
        selectmain.on("change",function(){
            setTimeout(function(){
                my_name = $("#field2_subform_name"); //Get subform value
                my_country = $("#field2_subform_country");
                my_date = $("#field2_subform_date");
                var field1 = FormUtil.getField("field3"); //Get field of form
                var field2 = FormUtil.getField("field4");
                $(field1).val(my_name.val()); //Set field to value of subform
                $(field2).val(my_country.val());
            },1200);
        });
    })
</script>

Now is working fine.