calculate days between two dates

Script
let date1 = '2020-01-01'
let date2 = '2020-01-10'

//@return number of days
function daysBetween(date1, date2){
  let oneDay = 24 * 60 * 60 * 1000;
  let date1 = new Date(date1);
  let date2 = new Date(date2);
  let diffDays = Math.round(Math.abs((date1.getTime() - date2.getTime())/(oneDay)));
  return diffDays;
}

daysBetween(date1, date2)