Check if year is leap year in javascript

The function checks if February has 29 days. If it does, then we have a leap year.

ES5

function isLeap(year) {
  return new Date(year, 1, 29).getDate() === 29;
}

ES6

const isLeap = year => new Date(year, 1, 29).getDate() === 29;

Result

isLeap(1004) // true
isLeap(1001) // false

A faster solution is provided by Kevin P. Rice here:https://stackoverflow.com/a/11595914/5535820 So here's the code:

function leapYear(year)
{
    return (year & 3) == 0 && ((year % 25) != 0 || (year & 15) == 0);
}

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

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