1function isLeap(year) {
2   if (year % 4 === 0) {
3      if (year % 100 === 0){
4         if (year % 400 == 0){
5            return ("Leap year.");
6         } else {
7            return ("Not leap year.");
8         }
9      } else {
10         return ("Leap year.");
11      }
12   } else{
13      return ("Not leap year.");
14   }
15}

1function isLeapYear(year) {
2  if (year % 400 === 0) return true;
3  if (year % 100 === 0) return false;
4  return year % 4 === 0;
5}
6

1function isLeapYear(year){
2	if(year % 400 === 0 && year % 4 === 0){
3      return true
4    } else {
5      return false
6    }
7}