#### Date Day Difference

E
S
```/*
DateDayDifference Method
------------------------
DateDayDifference method calculates the number of days between two dates.

Algorithm & Explanation : https://ncalculators.com/time-date/date-difference-calculator.htm
*/

// Internal method for make calculations easier
const isLeap = (year) => {
if (year % 400 === 0) return true
else if (year % 100 === 0) return false
else if (year % 4 === 0) return true
else return false
}
const DateToDay = (dd, mm, yyyy) => {
return Math.floor((365 * (yyyy - 1)) + ((yyyy - 1) / 4) - ((yyyy - 1) / 100) + ((yyyy - 1) / 400) + dd + (((367 * mm) - 362) / 12) + (mm <= 2 ? 0 : isLeap(yyyy) ? -1 : -2))
}

const DateDayDifference = (date1, date2) => {
// firstly, check that both input are string or not.
if (typeof date1 !== 'string' && typeof date2 !== 'string') {
return new TypeError('Argument is not a string.')
}
// extract the first date
const [firstDateDay, firstDateMonth, firstDateYear] = date1.split('/').map((ele) => Number(ele))
// extract the second date
const [secondDateDay, secondDateMonth, secondDateYear] = date2.split('/').map((ele) => Number(ele))
// check the both data are valid or not.
if (firstDateDay < 0 || firstDateDay > 31 ||
firstDateMonth > 12 || firstDateMonth < 0 ||
secondDateDay < 0 || secondDateDay > 31 ||
secondDateMonth > 12 || secondDateMonth < 0) {
return new TypeError('Date is not valid.')
}
return Math.abs(DateToDay(secondDateDay, secondDateMonth, secondDateYear) - DateToDay(firstDateDay, firstDateMonth, firstDateYear))
}

// Example : DateDayDifference('17/08/2002', '10/10/2020') => 6630

export { DateDayDifference }
```