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freddie2025's solution

to Leap in the JavaScript Track

Published at Mar 23 2020 · 0 comments
Test suite

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.


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.


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



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.


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.


import { isLeap } from './leap';

describe('A leap year', () => {
  test('year not divisible by 4 in common year', () => {

  xtest('year divisible by 2, not divisible by 4 in common year', () => {

  xtest('year divisible by 4, not divisible by 100 in leap year', () => {

  xtest('year divisible by 4 and 5 is still a leap year', () => {

  xtest('year divisible by 100, not divisible by 400 in common year', () => {

  xtest('year divisible by 100 but not by 3 is still not a leap year', () => {

  xtest('year divisible by 400 in leap year', () => {

  xtest('year divisible by 400 but not by 125 is still a leap year', () => {

  xtest('year divisible by 200, not divisible by 400 in common year', () => {
// This is only a SKELETON file for the 'Leap' exercise. It's been provided as a
// convenience to get you started writing code faster.

export const isLeap = (year) => {
    return (year % 4 === 0) && ((year % 100 !== 0) || (year % 400 === 0));

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