In this kata you should simply determine, whether a given year is a leap year or not

leapyear.js

Description:

In this kata you should simply determine, whether a given year is a leap year or not. In case you don't know the rules, here they are:

years divisible by 4 are leap years
but years divisible by 100 are no leap years
but years divisible by 400 are leap years
Additional Notes:

Only valid years (positive integers) will be tested, so you don't have to validate them
Examples can be found in the test fixture.

Solution 1.

function isLeapYear(year) {
  return (year % 100 !== 0 && year % 4 === 0) || year % 400 === 0;
}

Solution 2.

function isLeapYear(year) {
  return (year / 4) % 4 === 0;
}


Solution 3.

function isLeapYear(year) {
  function isDiv(num){
    return year/num === parseInt(year/num)
  }
  return isDiv(4) && !isDiv(100) || isDiv(400)
}

Solution 4.

function isLeapYear(year) {
  if(0 == year%400) return true;
  if(0 == year%100) return false;
  if(0 == year%4) return true;
  return false;
}