How to get the date difference between two jalali date (persianDatepicker) on clicking the second input date picker?

I use this https://github.com/behzadi/persianDatepicker script to show jalali date

I select date1 and date2 to from datepicker to my input

Code

<script>
$(document).ready(function() {
    $('.example').persianDatepicker({
    format: 'YYYY/MM/DD',
    observer: true,
    altField: '.observer-example-alt',
        autoClose: true,
});
  });
</script>

<input id="start-date" class="example" name="start-date"/>  
<input id="end-date" class="example" name="end-date"/>     
<input id="diff" class="example" name="diff"/>    

I want when I select date1 (id=”start-date”) and date 2 (id=”end-date”) it will immediately display in (id=”diff”) the difference between the two jalali dates

for example 1

date1= 1403/06/06 
date2= 1403/06/06  

result:

1 day

example 2

date1= 1403/06/06 
date2= 1403/06/07   

result:

2 days

i dont add what add in my javascript to earn my result

<script>
??????
??????
</script>