# PatrickMcSweeny's solution

## to Resistor Color Duo in the JavaScript Track

Published at Aug 18 2019 · 0 comments
Instructions
Test suite
Solution

#### Note:

This exercise has changed since this solution was written.

If you want to build something using a Raspberry Pi, you'll probably use resistors. For this exercise, you need to know two things about them:

• Each resistor has a resistance value.
• Resistors are small - so small in fact that if you printed the resistance value on them, it would be hard to read. To get around this problem, manufacturers print color-coded bands onto the resistors to denote their resistance values. Each band acts as a digit of a number. For example, if they printed a brown band (value 1) followed by a green band (value 5), it would translate to the number 15.

In this exercise, you are going to create a helpful program so that you don't have to remember the values of the bands. The program will take two colors as input, and output the correct number.

The band colors are encoded as follows:

• Black: 0
• Brown: 1
• Red: 2
• Orange: 3
• Yellow: 4
• Green: 5
• Blue: 6
• Violet: 7
• Grey: 8
• White: 9

## 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

Maud de Vries, Erik Schierboom https://github.com/exercism/problem-specifications/issues/1464

## Submitting Incomplete Solutions

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

### resistor-color-duo.spec.js

``````import { value } from './resistor-color-duo.js';

describe('Resistor Colors', () => {
test('Brown and black', () => {
expect(value(['brown', 'black'])).toEqual(10);
});

xtest('Blue and grey', () => {
expect(value(['blue', 'grey'])).toEqual(68);
});

xtest('Yellow and violet', () => {
expect(value(['yellow', 'violet'])).toEqual(47);
});

xtest('Orange and orange', () => {
expect(value(['orange', 'orange'])).toEqual(33);
});
});``````
``````const COLORS = ["black", "brown", "red", "orange", "yellow", "green", "blue", "violet", "grey", "white"];

export const value = (colors) =>
Number(colors.map(color => COLORS.indexOf(color)).join(""));``````

### What can you learn from this solution?

A huge amount can be learned from reading other peopleโs code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

• What compromises have been made?