odin-default-js-exercises/06_leapYears/leapYears.js

const leapYears = function(year) {
    if (typeof(year) !== 'number')
        return 'ERROR';
    
    if((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0))
    {
        return true;
    }
    else
        return false;
};

// Do not edit below this line
module.exports = leapYears;