freeCodeCamp/curriculum/challenges/english/08-coding-interview-prep/rosetta-code/leap-year.md

---
id: 5a23c84252665b21eecc7ede
title: Leap year
challengeType: 5
---

## Description
<section id='description'>
Determine whether a given year is a leap year in the Gregorian calendar.
</section>

## Instructions
<section id='instructions'>

</section>

## Tests
<section id='tests'>

``` yml
tests:
  - text: <code>isLeapYear</code> should be a function.
    testString: assert(typeof isLeapYear == 'function', '<code>isLeapYear</code> should be a function.');
  - text: <code>isLeapYear()</code> should return a boolean.
    testString: assert(typeof isLeapYear(2018) == 'boolean', '<code>isLeapYear()</code> should return a boolean.');
  - text: <code>isLeapYear(2018)</code> should return <code>false</code>.
    testString: assert.equal(isLeapYear(2018), false, '<code>isLeapYear(2018)</code> should return <code>false</code>.');
  - text: <code>isLeapYear(2016)</code> should return <code>true</code>.
    testString: assert.equal(isLeapYear(2016), true, '<code>isLeapYear(2016)</code> should return <code>true</code>.');
  - text: <code>isLeapYear(2000)</code> should return <code>true</code>.
    testString: assert.equal(isLeapYear(2000), true, '<code>isLeapYear(2000)</code> should return <code>true</code>.');
  - text: <code>isLeapYear(1900)</code> should return <code>false</code>.
    testString: assert.equal(isLeapYear(1900), false, '<code>isLeapYear(1900)</code> should return <code>false</code>.');
  - text: <code>isLeapYear(1996)</code> should return <code>true</code>.
    testString: assert.equal(isLeapYear(1996), true, '<code>isLeapYear(1996)</code> should return <code>true</code>.');
  - text: <code>isLeapYear(1800)</code> should return <code>false</code>.
    testString: assert.equal(isLeapYear(1800), false, '<code>isLeapYear(1800)</code> should return <code>false</code>.');
```

</section>

## Challenge Seed
<section id='challengeSeed'>
<div id='js-seed'>

```js
function isLeapYear(year) {
  // Good luck!
}
```

</div>
</section>

## Solution
<section id='solution'>

```js
function isLeapYear (year) {
  return (year % 100 === 0) ? (year % 400 === 0) : (year % 4 === 0);
};
```

</section>