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rootulp's solution

to ETL in the JavaScript Track

Published at Jul 13 2018 · 0 comments
Test suite


This solution was written on an old version of Exercism. The tests below might not correspond to the solution code, and the exercise may have changed since this code was written.

We are going to do the Transform step of an Extract-Transform-Load.


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.


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.


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


Running the test suite

The provided test suite uses Jasmine. You can install it by opening a terminal window and running the following command:

npm install -g jasmine

Run the test suite from the exercise directory with:

jasmine etl.spec.js

In many test suites all but the first test have been marked "pending". Once you get a test passing, activate the next one by changing xit to it.


The Jumpstart Lab team http://jumpstartlab.com

Submitting Incomplete Solutions

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


var ETL = require('./etl');

describe('Transform', function () {
  var etl = new ETL();

  it('transforms one value', function () {
    var old = { 1: ['A'] };
    var expected = { a: 1 };


  xit('transforms more values', function () {
    var old = { 1: ['A', 'E', 'I', 'O', 'U'] };
    var expected = { a: 1, e: 1, i: 1, o: 1, u: 1 };


  xit('transforms more keys', function () {
    var old = { 1: ['A', 'E'], 2: ['D', 'G'] };
    var expected = { a: 1, e: 1, d: 2, g: 2 };


  xit('transforms a full dataset', function () {
    var 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' ]
    var 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

function transform(legacy_data) {
  var new_data = {}

  for (var key in legacy_data) {
    if (legacy_data.hasOwnProperty(key)) {
      add(Number(key), legacy_data[key])

  function add(val, char_arr) {
    for (var i = 0; i < char_arr.length; i++) {
      new_data[char_arr[i].toLowerCase()] = val

  return new_data;

module.exports = transform

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