typescript difference between two dates

const date1 = new Date('7/13/2010');
const date2 = new Date('12/15/2010');
console.log(getDifferenceInDays(date1, date2));
console.log(getDifferenceInHours(date1, date2));
console.log(getDifferenceInMinutes(date1, date2));
console.log(getDifferenceInSeconds(date1, date2));

function getDifferenceInDays(date1, date2) {
  const diffInMs = Math.abs(date2 - date1);
  return diffInMs / (1000 * 60 * 60 * 24);
}

function getDifferenceInHours(date1, date2) {
  const diffInMs = Math.abs(date2 - date1);
  return diffInMs / (1000 * 60 * 60);
}

function getDifferenceInMinutes(date1, date2) {
  const diffInMs = Math.abs(date2 - date1);
  return diffInMs / (1000 * 60);
}

function getDifferenceInSeconds(date1, date2) {
  const diffInMs = Math.abs(date2 - date1);
  return diffInMs / 1000;
}

dayDiff(d1:Date, d2:Date)
  {
    var diff = Math.abs(date1.getTime() - date2.getTime());
    var diffDays = Math.ceil(diff / (1000 * 3600 * 24)); 
    return diffDays;
  }

for(let k = 0; k < this.bookingDetailsArrayRealObject.length; k++){
        let dateCheckOut = this.bookingDetailsArrayRealObject[k].package.chackout;
        let dateToBeCheckOut = new Date(dateCheckOut);
        let today = new Date();
        //let today_test = new Date();
        if(this.bookingDetailsArrayRealObject[k].status){
          if(dateToBeCheckOut < today){
            this.bookingIdsToBeUpdated.push(this.bookingDetailsArrayRealObject[k]._id);
            window.alert('true');
            console.log(today.toDateString());
            console.log(dateToBeCheckOut.toDateString());
            console.log(this.bookingDetailsArrayRealObject[k]);
          }
        }
      }