# How to check a Leap Year in JavaScript

In this tutorial, we are going to learn about how to check if a given year is a leap year or not in JavaScript.

## What is a Leap Year?

A leap year is a year that contains 366 days, where an extra day is added to February so that in a leap year February contains 29 days instead of 28.

A Leap year occurs in every 4 years.

## Checking leap year

Let’s write a function that is used to check if a given year is a leap year or not.

```
function isLeapYear(year){
return (year%4 === 0 && year%100 !==0 || year%400 === 0);}
console.log(isLeapYear(2020)); // true
console.log(isLeapYear(2019)); // false
```

The logic is if a given year is divisible by 4 and divisible by 100 but not divisible by 400 it is a common year else the given year is a leap year.

According to this logic, the years 2000 and 2400 are leap years, while 1700, 1800, 1900, 2100, 2200, 2300, and 2500 are not leap years.