Please, I don't know What is wrong....

$(document).ready(() => {
$('#calc').click(() => {
var d1 = $('#d1').val();
var d2 = $('#d2').val();
$('#dif').text(workingDaysBetweenDates(d1,d2));
});
});

//* Two working days and an sunday (not working day) */

var holidays = ['24-12-2019', '25-12-2019', '26-12-2019'];
var startDate = @Days/time out office;
var endDate = @Return to office;

// Validate input
if (endDate < startDate) {
return 0;
}

// Calculate days between dates
var millisecondsPerDay = 86400 * 1000; // Day in milliseconds
startDate.setHours(0, 0, 0, 1); // Start just after midnight
endDate.setHours(23, 59, 59, 999); // End just before midnight
var diff = endDate - startDate; // Milliseconds between datetime objects
var days = Math.ceil(diff / millisecondsPerDay);

// Subtract two weekend days for every week in between
var weeks = Math.floor(days / 7);
days -= weeks * 2;

// Handle special cases
var startDay = startDate.getDay();
var endDay = endDate.getDay();

// Remove weekend not previously removed.
if (startDay - endDay > 1) {
days -= 2;
}
// Remove start day if span starts on Sunday but ends before Saturday
if (startDay == 0 && endDay != 6) {
days--;
}
// Remove end day if span ends on Saturday but starts after Sunday
if (endDay == 6 && startDay != 0) {
days--;
}
/* Here is the code */

holidays.forEach(day => {
if ((day >= d0) && (day <= d1)) {
/* If it is not saturday (6) or sunday (0), substract it */
if ((parseDate(day).getDay() % 6) != 0) {
days--;
}
}
});
return days;
}

startDate == null || endDate == null ? "" : workingDaysBetweenDates( new Date(startDate) , new Date(endDate))