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# thekeele's solution

## to Leap in the JavaScript Track

Published at Jul 30 2019 · 0 comments
Instructions
Test suite
Solution

#### Note:

This exercise has changed since this solution was written.

Given a year, report if it is a leap year.

The tricky thing here is that a leap year in the Gregorian calendar occurs:

``````on every year that is evenly divisible by 4
except every year that is evenly divisible by 100
unless the year is also evenly divisible by 400
``````

For example, 1997 is not a leap year, but 1996 is. 1900 is not a leap year, but 2000 is.

## Notes

Though our exercise adopts some very simple rules, there is more to learn!

For a delightful, four minute explanation of the whole leap year phenomenon, go watch this youtube video.

## Setup

Go through the setup instructions for Javascript to install the necessary dependencies:

https://exercism.io/tracks/javascript/installation

## Requirements

Install assignment dependencies:

``````\$ npm install
``````

## Making the test suite pass

Execute the tests with:

``````\$ npm test
``````

In the test suites all tests but the first have been skipped.

Once you get a test passing, you can enable the next one by changing `xtest` to `test`.

## Source

JavaRanch Cattle Drive, exercise 3 http://www.javaranch.com/leap.jsp

## Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

### leap.spec.js

``````import { isLeap } from './leap';

describe('A leap year', () => {
test('year not divisible by 4: common year', () => {
expect(isLeap(2015)).toBe(false);
});

xtest('year divisible by 4, not divisible by 100: leap year', () => {
expect(isLeap(2016)).toBe(true);
});

xtest('year divisible by 100, not divisible by 400: common year', () => {
expect(isLeap(2100)).toBe(false);
});

xtest('year divisible by 400: leap year', () => {
expect(isLeap(2000)).toBe(true);
});

xtest('year divisible by 200, not divisible by 400: common year', () => {
expect(isLeap(1800)).toBe(false);
});
});``````
``````export const isLeap = (year) => {
return (year % 4 == 0) && (year % 100 != 0) || (year % 400 == 0);
};``````