```
/**
* isLeapYear :: Number -> Boolean
*
* Check if a year is a leap year or not. A leap year is a year which has 366 days.
* For the extra +1 day the February month contains 29 days instead of 28 days.
*
* The logic behind the leap year is-
* 1. If the year is divisible by 400 then it is a leap year.
* 2. If it is not divisible by 400 but divisible by 100 then it is not a leap year.
* 3. If the year is not divisible by 400 but not divisible by 100 and divisible by 4 then a leap year.
* 4. Other cases except the describing ones are not a leap year.
*
* @param {number} year
* @returns {boolean} true if this is a leap year, false otherwise.
*/
export const isLeapYear = (year) => {
if (year % 400 === 0) return true
if (year % 100 === 0) return false
if (year % 4 === 0) return true
return false
}
```