how to calculate the number of days between two dates in javascript

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;
}function javascript (date1, date2) {
   let oned = 24 * 60 * 60 * 1000;
   return Math.ceil((date2 - date1) / oned);
}

function javascript(date1, date2) {
	return new Date(date2 - date1).getDate() - 1
}

function javascript(date1, date2) {
  return Math.ceil((date2 - date1) / 8.64e7);
}