add scale-generator exercise (#754)

* add scale-generator exercise

Author: seeksort

config.json

@@ -990,6 +990,19 @@
         "games"
       ]
     },
+    {
+      "slug": "scale-generator",
+      "uuid": "b9c586e8-998b-4f5d-ab98-a08be29a9f19",
+      "core": false,
+      "unlocked_by": "pangram",
+      "difficulty": 3,
+      "topics": [
+        "loops",
+        "pattern_recognition",
+        "strings",
+        "arrays"
+      ]
+    },
     {
       "slug": "connect",
       "uuid": "2fa2c262-77ae-409b-bfd8-1d643faae772",

exercises/scale-generator/.eslintrc

@@ -0,0 +1,26 @@
+{
+  "root": true,
+  "parser": "babel-eslint",
+  "parserOptions": {
+    "ecmaVersion": 7,
+    "sourceType": "module"
+  },
+  "env": {
+    "es6": true,
+    "node": true,
+    "jest": true
+  },
+  "extends": [
+    "eslint:recommended",
+    "plugin:import/errors",
+    "plugin:import/warnings"
+  ],
+  "rules": {
+    "linebreak-style": "off",
+
+    "import/extensions": "off",
+    "import/no-default-export": "off",
+    "import/no-unresolved": "off",
+    "import/prefer-default-export": "off"
+  }
+}

exercises/scale-generator/README.md

@@ -0,0 +1,82 @@
+# Scale Generator
+
+Given a tonic, or starting note, and a set of intervals, generate
+the musical scale starting with the tonic and following the
+specified interval pattern.
+
+Scales in Western music are based on the chromatic (12-note) scale. This
+scale can be expressed as the following group of pitches:
+
+A, A#, B, C, C#, D, D#, E, F, F#, G, G#
+
+A given sharp note (indicated by a #) can also be expressed as the flat
+of the note above it (indicated by a b) so the chromatic scale can also be
+written like this:
+
+A, Bb, B, C, Db, D, Eb, E, F, Gb, G, Ab
+
+The major and minor scale and modes are subsets of this twelve-pitch
+collection. They have seven pitches, and are called diatonic scales.
+The collection of notes in these scales is written with either sharps or
+flats, depending on the tonic. Here is a list of which are which:
+
+No Sharps or Flats:
+C major
+a minor
+
+Use Sharps:
+G, D, A, E, B, F# major
+e, b, f#, c#, g#, d# minor
+
+Use Flats:
+F, Bb, Eb, Ab, Db, Gb major
+d, g, c, f, bb, eb minor
+
+The diatonic scales, and all other scales that derive from the
+chromatic scale, are built upon intervals. An interval is the space
+between two pitches.
+
+The simplest interval is between two adjacent notes, and is called a
+"half step", or "minor second" (sometimes written as a lower-case "m").
+The interval between two notes that have an interceding note is called
+a "whole step" or "major second" (written as an upper-case "M"). The
+diatonic scales are built using only these two intervals between
+adjacent notes.
+
+Non-diatonic scales can contain other intervals.  An "augmented first"
+interval, written "A", has two interceding notes (e.g., from A to C or
+Db to E). There are also smaller and larger intervals, but they will not
+figure into this exercise.
+
+## Setup
+
+Go through the setup instructions for Javascript to install the necessary
+dependencies:
+
+[https://exercism.io/tracks/javascript/installation](https://exercism.io/tracks/javascript/installation)
+
+## Requirements
+
+Install assignment dependencies:
+
+```bash
+$ npm install
+```
+
+## Making the test suite pass
+
+Execute the tests with:
+
+```bash
+$ 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 Incomplete Solutions
+
+It's possible to submit an incomplete solution so you can see how others have
+completed the exercise.

exercises/scale-generator/babel.config.js

@@ -0,0 +1,14 @@
+module.exports = {
+  presets: [
+    [
+      '@babel/env',
+      {
+        targets: {
+          node: 'current',
+        },
+        useBuiltIns: false,
+      },
+
+    ],
+  ],
+};

exercises/scale-generator/example.js

@@ -0,0 +1,33 @@
+export class Scale {
+  constructor(tonic) {
+    this.INTERVAL_STEPS = ['m', 'M', 'A']
+    this.SHARPS_SCALE = ['A', 'A#', 'B', 'C', 'C#', 'D', 'D#', 'E', 'F', 'F#', 'G', 'G#']
+    this.FLATS_SCALE = ['A', 'Bb', 'B', 'C', 'Db', 'D', 'Eb', 'E', 'F', 'Gb', 'G', 'Ab']
+    this.USE_FLATS = ['F', 'Bb', 'Eb', 'Ab', 'Db', 'Gb', 'd', 'g', 'c', 'f', 'bb', 'eb']
+
+    this.tonic = tonic.slice(0, 1).toUpperCase() + tonic.slice(1);
+    // note use of original tonic argument
+    this.chromaticScale = this.USE_FLATS.includes(tonic) ? this.FLATS_SCALE : this.SHARPS_SCALE
+  }
+
+  chromatic() {
+    return this.reorderChromaticScale()
+  }
+
+  interval(intervals) {
+    const scale = this.reorderChromaticScale()
+    const result = []
+    let currentIndex = 0
+
+    for (const step of intervals) {
+      result.push(scale[currentIndex])
+      currentIndex = currentIndex + (this.INTERVAL_STEPS.indexOf(step) + 1)
+    }
+    return result
+  }
+
+  reorderChromaticScale() {
+    const tonicIndex = this.chromaticScale.indexOf(this.tonic)
+    return this.chromaticScale.slice(tonicIndex).concat(this.chromaticScale.slice(0, tonicIndex))
+  }
+}

exercises/scale-generator/package.json

@@ -0,0 +1,35 @@
+{
+  "name": "exercism-javascript",
+  "description": "Exercism exercises in Javascript.",
+  "author": "Katrina Owen",
+  "private": true,
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/exercism/javascript"
+  },
+  "devDependencies": {
+    "@babel/cli": "^7.5.5",
+    "@babel/core": "^7.5.5",
+    "@babel/preset-env": "^7.5.5",
+    "@types/jest": "^24.0.16",
+    "@types/node": "^12.6.8",
+    "babel-eslint": "^10.0.2",
+    "babel-jest": "^24.8.0",
+    "eslint": "^6.1.0",
+    "eslint-plugin-import": "^2.18.2",
+    "jest": "^24.8.0"
+  },
+  "jest": {
+    "modulePathIgnorePatterns": [
+      "package.json"
+    ]
+  },
+  "scripts": {
+    "test": "jest --no-cache ./*",
+    "watch": "jest --no-cache --watch ./*",
+    "lint": "eslint .",
+    "lint-test": "eslint . && jest --no-cache ./* "
+  },
+  "license": "MIT",
+  "dependencies": {}
+}

exercises/scale-generator/scale-generator.js

@@ -0,0 +1,18 @@
+//
+// This is only a SKELETON file for the 'Scale Generator' exercise. It's been provided as a
+// convenience to get you started writing code faster.
+//
+
+export class Scale {
+  constructor(tonic) {
+    throw new Error("Remove this statement and implement this function");
+  }
+
+  chromatic() {
+    throw new Error("Remove this statement and implement this function");
+  }
+
+  interval(intervals) {
+    throw new Error("Remove this statement and implement this function");
+  }
+}

exercises/scale-generator/scale-generator.spec.js

@@ -0,0 +1,92 @@
+import { Scale } from './scale-generator'
+
+describe('ScaleGenerator', () => {
+  describe('Chromatic scales', () => {
+    test('Chromatic scale with sharps', () => {
+      const expected = ['C', 'C#', 'D', 'D#', 'E', 'F', 'F#', 'G', 'G#', 'A', 'A#', 'B']
+      expect(new Scale('C').chromatic()).toEqual(expected)
+    })
+
+    xtest('Chromatic scale with flats', () => {
+      const expected = ['F', 'Gb', 'G', 'Ab', 'A', 'Bb', 'B', 'C', 'Db', 'D', 'Eb', 'E']
+      expect(new Scale('F').chromatic()).toEqual(expected)
+    })
+  })
+
+  describe('Scales with specified intervals', () => {
+    xtest('Simple major scale', () => {
+      const expected = ['C', 'D', 'E', 'F', 'G', 'A', 'B']
+      expect(new Scale('C').interval('MMmMMMm')).toEqual(expected)
+    })
+
+    xtest('Major scale with sharps', () => {
+      const expected = ['G', 'A', 'B', 'C', 'D', 'E', 'F#']
+      expect(new Scale('G').interval('MMmMMMm')).toEqual(expected)
+    })
+
+    xtest('Major scale with flats', () => {
+      const expected = ['F', 'G', 'A', 'Bb', 'C', 'D', 'E']
+      expect(new Scale('F').interval('MMmMMMm')).toEqual(expected)
+    })
+
+    xtest('Minor scale with sharps', () => {
+      const expected = ['F#', 'G#', 'A', 'B', 'C#', 'D', 'E']
+      expect(new Scale('f#').interval('MmMMmMM')).toEqual(expected)
+    })
+
+    xtest('Minor scale with flats', () => {
+      const expected = ['Bb', 'C', 'Db', 'Eb', 'F', 'Gb', 'Ab']
+      expect(new Scale('bb').interval('MmMMmMM')).toEqual(expected)
+    })
+
+    xtest('Dorian mode', () => {
+      const expected = ['D', 'E', 'F', 'G', 'A', 'B', 'C']
+      expect(new Scale('d').interval('MmMMMmM')).toEqual(expected)
+    })
+
+    xtest('Mixolydian mode', () => {
+      const expected = ['Eb', 'F', 'G', 'Ab', 'Bb', 'C', 'Db']
+      expect(new Scale('Eb').interval('MMmMMmM')).toEqual(expected)
+    })
+
+    xtest('Lydian mode', () => {
+      const expected = ['A', 'B', 'C#', 'D#', 'E', 'F#', 'G#']
+      expect(new Scale('a').interval('MMMmMMm')).toEqual(expected)
+    })
+
+    xtest('Phrygian mode', () => {
+      const expected = ['E', 'F', 'G', 'A', 'B', 'C', 'D']
+      expect(new Scale('e').interval('mMMMmMM')).toEqual(expected)
+    })
+
+    xtest('Locrian mode', () => {
+      const expected = ['G', 'Ab', 'Bb', 'C', 'Db', 'Eb', 'F']
+      expect(new Scale('g').interval('mMMmMMM')).toEqual(expected)
+    })
+
+    xtest('Harmonic minor', () => {
+      const expected = ['D', 'E', 'F', 'G', 'A', 'Bb', 'Db']
+      expect(new Scale('d').interval('MmMMmAm')).toEqual(expected)
+    })
+
+    xtest('Octatonic', () => {
+      const expected = ['C', 'D', 'D#', 'F', 'F#', 'G#', 'A', 'B']
+      expect(new Scale('C').interval('MmMmMmMm')).toEqual(expected)
+    })
+
+    xtest('Hexatonic', () => {
+      const expected = ['Db', 'Eb', 'F', 'G', 'A', 'B']
+      expect(new Scale('Db').interval('MMMMMM')).toEqual(expected)
+    })
+
+    xtest('Pentatonic', () => {
+      const expected = ['A', 'B', 'C#', 'E', 'F#']
+      expect(new Scale('A').interval('MMAMA')).toEqual(expected)
+    })
+
+    xtest('Enigmatic', () => {
+      const expected = ['G', 'G#', 'B', 'C#', 'D#', 'F', 'F#']
+      expect(new Scale('G').interval('mAMMMmm')).toEqual(expected)
+    })
+  })
+})