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PatrickMcSweeny's solution

to Space Age in the JavaScript Track

Published at Aug 20 2019 · 0 comments
Instructions
Test suite
Solution

Given an age in seconds, calculate how old someone would be on:

  • Earth: orbital period 365.25 Earth days, or 31557600 seconds
  • Mercury: orbital period 0.2408467 Earth years
  • Venus: orbital period 0.61519726 Earth years
  • Mars: orbital period 1.8808158 Earth years
  • Jupiter: orbital period 11.862615 Earth years
  • Saturn: orbital period 29.447498 Earth years
  • Uranus: orbital period 84.016846 Earth years
  • Neptune: orbital period 164.79132 Earth years

So if you were told someone were 1,000,000,000 seconds old, you should be able to say that they're 31.69 Earth-years old.

If you're wondering why Pluto didn't make the cut, 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

Partially inspired by Chapter 1 in Chris Pine's online Learn to Program tutorial. http://pine.fm/LearnToProgram/?Chapter=01

Submitting Incomplete Solutions

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

space-age.spec.js

import { age } from './space-age';

describe('Space Age', () => {
  test('age on Earth', () => {
    expect(age('earth', 1000000000)).toEqual(31.69);
  });

  xtest('age on Mercury', () => {
    expect(age('mercury', 2134835688)).toEqual(280.88);
  });

  xtest('age on Venus', () => {
    expect(age('venus', 189839836)).toEqual(9.78);
  });

  xtest('age on Mars', () => {
    expect(age('mars', 2129871239)).toEqual(35.88);
  });

  xtest('age on Jupiter', () => {
    expect(age('jupiter', 901876382)).toEqual(2.41);
  });

  xtest('age on Saturn', () => {
    expect(age('saturn', 2000000000)).toEqual(2.15);
  });

  xtest('age on Uranus', () => {
    expect(age('uranus', 1210123456)).toEqual(0.46);
  });

  xtest('age on Neptune', () => {
    expect(age('neptune', 1821023456)).toEqual(0.35);
  });
});
const SECONDS_PER_EARTH_YEAR = 31557600;

const ORBITAL_PERIODS = {
  mercury: 0.2408467,
  venus: 0.61519726,
  earth: 1,
  mars: 1.8808158,
  jupiter: 11.862615,
  saturn: 29.447498,
  uranus: 84.016846,
  neptune: 164.79132
};

export const age = (planet, seconds) =>
  roundTwo(ageOnEarth(seconds) / ORBITAL_PERIODS[planet]);

const ageOnEarth = seconds =>
  seconds / SECONDS_PER_EARTH_YEAR;

const roundTwo = number =>
  Math.round(number * 100) / 100;

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