Add exercise ETL with solution for it

Author: programmiri

etl/.eslintrc

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+{
+  "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"
+  }
+}

etl/README.md

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+# ETL
+
+We are going to do the `Transform` step of an Extract-Transform-Load.
+
+### ETL
+
+Extract-Transform-Load (ETL) is a fancy way of saying, "We have some crufty, legacy data over in this system, and now we need it in this shiny new system over here, so
+we're going to migrate this."
+
+(Typically, this is followed by, "We're only going to need to run this
+once." That's then typically followed by much forehead slapping and
+moaning about how stupid we could possibly be.)
+
+### The goal
+
+We're going to extract some scrabble scores from a legacy system.
+
+The old system stored a list of letters per score:
+
+- 1 point: "A", "E", "I", "O", "U", "L", "N", "R", "S", "T",
+- 2 points: "D", "G",
+- 3 points: "B", "C", "M", "P",
+- 4 points: "F", "H", "V", "W", "Y",
+- 5 points: "K",
+- 8 points: "J", "X",
+- 10 points: "Q", "Z",
+
+The shiny new scrabble system instead stores the score per letter, which
+makes it much faster and easier to calculate the score for a word. It
+also stores the letters in lower-case regardless of the case of the
+input letters:
+
+- "a" is worth 1 point.
+- "b" is worth 3 points.
+- "c" is worth 3 points.
+- "d" is worth 2 points.
+- Etc.
+
+Your mission, should you choose to accept it, is to transform the legacy data
+format to the shiny new format.
+
+### Notes
+
+A final note about scoring, Scrabble is played around the world in a
+variety of languages, each with its own unique scoring table. For
+example, an "E" is scored at 2 in the Māori-language version of the
+game while being scored at 4 in the Hawaiian-language version.
+
+## 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`.
+
+## Source
+
+The Jumpstart Lab team [http://jumpstartlab.com](http://jumpstartlab.com)
+
+## Submitting Incomplete Solutions
+
+It's possible to submit an incomplete solution so you can see how others have
+completed the exercise.

etl/babel.config.js

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

etl/etl.js

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+export const transform = (oldMap) => {
+	return Object.keys(oldMap).reduce((acc, curr) => {
+		oldMap[curr].forEach((letter) => {
+			acc[letter.toLowerCase()] = Number(curr);
+		});
+		return acc;
+	}, {});
+};

etl/etl.spec.js

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+import { transform } from './etl';
+
+describe('Transform', () => {
+  test('transforms one value', () => {
+    const old = { 1: ['A'] };
+    const expected = { a: 1 };
+
+    expect(transform(old)).toEqual(expected);
+  });
+
+  test('transforms more values', () => {
+    const old = { 1: ['A', 'E', 'I', 'O', 'U'] };
+    const expected = {
+      a: 1,
+      e: 1,
+      i: 1,
+      o: 1,
+      u: 1,
+    };
+
+    expect(transform(old)).toEqual(expected);
+  });
+
+  test('transforms more keys', () => {
+    const old = { 1: ['A', 'E'], 2: ['D', 'G'] };
+    const expected = {
+      a: 1,
+      e: 1,
+      d: 2,
+      g: 2,
+    };
+
+    expect(transform(old)).toEqual(expected);
+  });
+
+  test('transforms a full dataset', () => {
+    const old = {
+      1: ['A', 'E', 'I', 'O', 'U', 'L', 'N', 'R', 'S', 'T'],
+      2: ['D', 'G'],
+      3: ['B', 'C', 'M', 'P'],
+      4: ['F', 'H', 'V', 'W', 'Y'],
+      5: ['K'],
+      8: ['J', 'X'],
+      10: ['Q', 'Z'],
+    };
+    const expected = {
+      a: 1,
+      b: 3,
+      c: 3,
+      d: 2,
+      e: 1,
+      f: 4,
+      g: 2,
+      h: 4,
+      i: 1,
+      j: 8,
+      k: 5,
+      l: 1,
+      m: 3,
+      n: 1,
+      o: 1,
+      p: 3,
+      q: 10,
+      r: 1,
+      s: 1,
+      t: 1,
+      u: 1,
+      v: 4,
+      w: 4,
+      x: 8,
+      y: 4,
+      z: 10,
+    };
+
+    expect(transform(old)).toEqual(expected);
+  });
+});

etl/package.json

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+{
+  "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": {}
+}