Air Datepicker - calculate the number of days in the range of selected dates

To select a date range, I use the Air Datepicker plugin.

To connect the plugin, I use CDN:

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<link href="https://cdnjs.cloudflare.com/ajax/libs/air-datepicker/2.2.3/css/datepicker.min.css" rel="stylesheet" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/air-datepicker/2.2.3/js/datepicker.min.js"></script>    

Plugin Initialization:

var maxdate = new Date();
    maxdate.setDate(maxdate.getDate() + 14);
    $('#datepicker').datepicker({
        language: 'en',
        autoClose: 'true',
        clearButton: 'true',
        minDate: new Date(),
        maxDate: maxdate
    })

HTML Code:

<input type='text' id='datepicker' data-range="true" data-multiple-dates-separator=" - " data-language="en" />

How to calculate the number of days in the range of selected dates?

For example:

You have chosen - 5 days

UPDATE: I found the appropriate code, but it is for the jQuery UI Datepicker:

function showDays() {
var start = $('#arr_date').datepicker('getDate');
var end = $('#dep_date').datepicker('getDate');
if (!start || !end) return;
var days = (end - start) / 1000 / 60 / 60 / 24;
$('#num_nights').val(days);
}

$("#arr_date").datepicker({
dateFormat: 'dd-mm-yy',
onSelect: showDays,
 onClose: function( selectedDate ) {
     var dParts = selectedDate.split('-');
     var in30Days = new Date(dParts[2] + '/' +
                    dParts[1] + '/' +
                    (+dParts[0] + 30)
           );

$( "#dep_date" ).datepicker( "option", "minDate", in30Days );
}
});
$("#dep_date").datepicker({
dateFormat: 'dd-mm-yy',
onSelect: showDays,

});

HTML Code:

<p>Choose your dates.</p><br/>
Start Date <input type="text" id="arr_date"><br/>
End Date   <input type="text" id="dep_date"><br/>
No of Days       <input type="text" id="num_nights" readonly>

How to make it work Air Datepicker?

Need your help! Thanks!

You can count no days by this way :

function parseDate(str) {
    var mdy = str.split('/');
    return new Date(mdy[2], mdy[0]-1, mdy[1]);
}

function datediff(first, second) {
    return Math.round((second-first)/(1000*60*60*24));
}

$(function() {
  var myDatepicker =  $('#count_days').datepicker({
      language: 'en',
      range:true,
      multipleDatesSeparator : '-',
      onSelect: function onSelect(selectedDates) {
       console.log(selectedDates);
        if(selectedDates !== undefined && selectedDates != '' && selectedDates.indexOf('-') > -1){
        var mdy = selectedDates.split('-');
         $("#arr_date").val(mdy[0]);
      $("#dep_date").val(mdy[1]);
      $("#num_nights").val(datediff(parseDate(mdy[0]), parseDate(mdy[1])));
        }
      }
  })
});

<input type="text" name="count_days" id="count_days"class="datepicker-here"/>

<!--Date Format is like this : 03/01/2019 -->

<p>Choose your dates.</p><br/>
Start Date <input type="text" id="arr_date"><br/>
End Date   <input type="text" id="dep_date"><br/>
No of Days       <input type="text" id="num_nights" readonly>