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jimijos's solution

to Armstrong Numbers in the JavaScript Track

Published at May 06 2021 · 0 comments
Instructions
Test suite
Solution

An Armstrong number is a number that is the sum of its own digits each raised to the power of the number of digits.

For example:

• 9 is an Armstrong number, because 9 = 9^1 = 9
• 10 is not an Armstrong number, because 10 != 1^2 + 0^2 = 1
• 153 is an Armstrong number, because: 153 = 1^3 + 5^3 + 3^3 = 1 + 125 + 27 = 153
• 154 is not an Armstrong number, because: 154 != 1^3 + 5^3 + 4^3 = 1 + 125 + 64 = 190

Write some code to determine whether a number is an Armstrong number.

Setup

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

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

Requirements

Please cd into exercise directory before running all below commands.

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.

Submitting Solutions

Once you have a solution ready, you can submit it using:

exercism submit armstrong-numbers.js

Submitting Incomplete Solutions

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

Exercise Source Credits

armstrong-numbers.spec.js

import { isArmstrongNumber } from './armstrong-numbers';

describe('Armstrong Numbers', () => {
test('Zero is an Armstrong number', () => {
expect(isArmstrongNumber(0)).toEqual(true);
});

xtest('Single digit numbers are Armstrong numbers', () => {
expect(isArmstrongNumber(5)).toEqual(true);
});

xtest('There are no 2 digit Armstrong numbers', () => {
expect(isArmstrongNumber(10)).toEqual(false);
});

xtest('Three digit number that is an Armstrong number', () => {
expect(isArmstrongNumber(153)).toEqual(true);
});

xtest('Three digit number that is not an Armstrong number', () => {
expect(isArmstrongNumber(100)).toEqual(false);
});

xtest('Four digit number that is an Armstrong number', () => {
expect(isArmstrongNumber(9474)).toEqual(true);
});

xtest('Four digit number that is not an Armstrong number', () => {
expect(isArmstrongNumber(9475)).toEqual(false);
});

xtest('Seven digit number that is an Armstrong number', () => {
expect(isArmstrongNumber(9926315)).toEqual(true);
});

xtest('Seven digit number that is not an Armstrong number', () => {
expect(isArmstrongNumber(9926314)).toEqual(false);
});
});
//
// This is only a SKELETON file for the 'Armstrong Numbers' exercise. It's been provided as a
// convenience to get you started writing code faster.
//

export const isArmstrongNumber = (num) =>
Number(
[...String(num)].reduce(
(acc, i) => (acc += Number(i) ** String(num).length),
0
)
) === num;