//Easiest Leap-year condition
function isLeapyear(year){
if(year%4==0 || year%400==0 && year%1000!=0){
return true;
}
else{
return false;
}
}
const my_year = isLeapyear(1999); //Tip: 2000 is a leap year.
console.log('My year is', my_year );