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[New Exercise] Parallel letter frequency (exercism#2379)
* Auto-generated files for parallel-letter-frequency exercise * Adding tests and example solution * Update proof.ci.js * Added some credits, prerequisites and fixed linting errors * formatting * Removing unrelated changes * Satisfying the CI checks, hopefully * Update exercises/practice/parallel-letter-frequency/parallel-letter-frequency.js Co-authored-by: Erik Schierboom <[email protected]> * adding an append to the docs * Update instructions.append.md --------- Co-authored-by: Erik Schierboom <[email protected]>
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Diff for: ‎config.json

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"basics"
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],
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"difficulty": 2
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},
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{
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"slug": "parallel-letter-frequency",
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"name": "Parallel Letter Frequency",
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"uuid": "63126f78-ba0d-4271-978d-49e9312f0db2",
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"practices": [],
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"prerequisites": [
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"strings",
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"regular-expressions",
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"rest-and-spread",
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"arrow-functions",
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"basics"
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],
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"difficulty": 7
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}
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]
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},

Diff for: ‎exercises/practice/parallel-letter-frequency/.docs/instructions.append.md

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# Instructions append
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Due to the single-threaded nature of Javascript, code that appears to execute in parallel,
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such as `async functions` or `Promises`, actually execute concurrently.
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Such solutions will pass all the tests, even though they do not meet the requrement for parallel execution.
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## Concurency vs. Parallelism
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Here's a quick definition for each that illustrates the diferences between the two:
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- Concurrency is when two or more tasks can start, run and complete in overlapping time periods, being executed by the same processing unit.
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- Parallelism is when two or more tasks can start and run at the same time, being executed independently of eachother by separate processing units.
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## Parallelism in Javascript
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Even though Javascript by default is single-threaded, there is a way to execute code non-concurently,
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through the [Web Worker API](https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API).
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As described by MDN:
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> Web Workers makes it possible to run a script operation in a background thread separate from the main execution thread of a web application.
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Here's a simple demo (taken from [here](https://medium.com/@ns-tech-learn/what-is-a-web-worker-how-to-use-it-and-example-2273de521f04))
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```js
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// main.js
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const myWorker = new Worker('worker.js');
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myWorker.postMessage(5);
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myWorker.onmessage = function (event) {
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console.log('Received result from worker:', event.data);
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};
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```
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```js
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// worker.js
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onmessage = function (event) {
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console.log('Received number from main thread:', event.data);
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// Perform computation
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const result = event.data * 2;
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// Send result back to the main thread
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postMessage(result);
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};
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```
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As a stretch goal, consider if your implementation can be adapted to make use of `Web workers`.
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---
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## Further reading
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- [MDN demo](https://mdn.github.io/dom-examples/web-workers/simple-web-worker/)
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- [MDN - Web Workers](https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Using_web_workers)
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- [Article about multi-threading in JS](https://medium.com/techtrument/multithreading-javascript-46156179cf9a)
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- [Web Worker primer](https://medium.com/@ns-tech-learn/what-is-a-web-worker-how-to-use-it-and-example-2273de521f04)

Diff for: ‎exercises/practice/parallel-letter-frequency/.docs/instructions.md

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# Instructions
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Count the frequency of letters in texts using parallel computation.
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Parallelism is about doing things in parallel that can also be done sequentially.
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A common example is counting the frequency of letters.
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Create a function that returns the total frequency of each letter in a list of texts and that employs parallelism.

Diff for: ‎exercises/practice/parallel-letter-frequency/.eslintrc

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{
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"root": true,
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"extends": "@exercism/eslint-config-javascript",
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"env": {
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"jest": true
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},
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"overrides": [
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{
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"files": [".meta/proof.ci.js", ".meta/exemplar.js", "*.spec.js"],
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"excludedFiles": ["custom.spec.js"],
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"extends": "@exercism/eslint-config-javascript/maintainers"
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}
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]
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}

Diff for: ‎exercises/practice/parallel-letter-frequency/.gitignore

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/node_modules
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/bin/configlet
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/bin/configlet.exe
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/pnpm-lock.yaml
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/yarn.lock

Diff for: ‎exercises/practice/parallel-letter-frequency/.meta/config.json

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{
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"authors": [
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"Cool-Katt"
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],
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"files": {
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"solution": [
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"parallel-letter-frequency.js"
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],
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"test": [
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"parallel-letter-frequency.spec.js"
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],
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"example": [
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".meta/proof.ci.js"
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]
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},
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"blurb": "Count the frequency of letters in texts using parallel computation."
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}

Diff for: ‎exercises/practice/parallel-letter-frequency/.meta/proof.ci.js

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export const parallelLetterFrequency = (texts) => {
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let result = {};
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let formatedTexts = texts
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.map((x) => x.toLowerCase().match(/\p{Letter}+/gu) ?? [])
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.flat();
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Promise.all(formatedTexts.map((t) => processSingleText(t, result)));
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return result;
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};
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const processSingleText = (text, result) => {
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return new Promise((resolve) => {
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let res = [...text].reduce((acc, cur) => {
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acc[cur] = (acc[cur] || 0) + 1;
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return acc;
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}, result);
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resolve(res);
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});
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};

Diff for: ‎exercises/practice/parallel-letter-frequency/.meta/tests.toml

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# This is an auto-generated file.
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#
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# Regenerating this file via `configlet sync` will:
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# - Recreate every `description` key/value pair
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# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications
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# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion)
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# - Preserve any other key/value pair
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#
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# As user-added comments (using the # character) will be removed when this file
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# is regenerated, comments can be added via a `comment` key.
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[c054d642-c1fa-4234-8007-9339f2337886]
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description = "no texts"
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[818031be-49dc-4675-b2f9-c4047f638a2a]
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description = "one text with one letter"
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[c0b81d1b-940d-4cea-9f49-8445c69c17ae]
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description = "one text with multiple letters"
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[708ff1e0-f14a-43fd-adb5-e76750dcf108]
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description = "two texts with one letter"
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[1b5c28bb-4619-4c9d-8db9-a4bb9c3bdca0]
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description = "two texts with multiple letters"
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[6366e2b8-b84c-4334-a047-03a00a656d63]
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description = "ignore letter casing"
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[92ebcbb0-9181-4421-a784-f6f5aa79f75b]
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description = "ignore whitespace"
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[bc5f4203-00ce-4acc-a5fa-f7b865376fd9]
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description = "ignore punctuation"
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[68032b8b-346b-4389-a380-e397618f6831]
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description = "ignore numbers"
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[aa9f97ac-3961-4af1-88e7-6efed1bfddfd]
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description = "Unicode letters"
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[7b1da046-701b-41fc-813e-dcfb5ee51813]
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description = "combination of lower- and uppercase letters, punctuation and white space"
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[4727f020-df62-4dcf-99b2-a6e58319cb4f]
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description = "large texts"
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[adf8e57b-8e54-4483-b6b8-8b32c115884c]
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description = "many small texts"

Diff for: ‎exercises/practice/parallel-letter-frequency/.npmrc

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audit=false

Diff for: ‎exercises/practice/parallel-letter-frequency/LICENSE

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MIT License
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Copyright (c) 2021 Exercism
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in all
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copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.

Diff for: ‎exercises/practice/parallel-letter-frequency/babel.config.js

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module.exports = {
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presets: ['@exercism/babel-preset-javascript'],
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plugins: [],
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};

Diff for: ‎exercises/practice/parallel-letter-frequency/package.json

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{
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"name": "@exercism/javascript-parallel-letter-frequency",
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"description": "Exercism practice exercise on parallel-letter-frequency",
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"author": "Katrina Owen",
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"contributors": [
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"Cool-Katt (https://github.com/Cool-Katt)",
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"Derk-Jan Karrenbeld <[email protected]> (https://derk-jan.com)",
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"Tejas Bubane (https://tejasbubane.github.io/)"
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],
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"private": true,
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"license": "MIT",
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"repository": {
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"type": "git",
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"url": "https://github.com/exercism/javascript",
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"directory": "exercises/practice/parallel-letter-frequency"
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},
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"devDependencies": {
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"@babel/core": "^7.23.0",
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"@exercism/babel-preset-javascript": "^0.2.1",
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"@exercism/eslint-config-javascript": "^0.6.0",
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"@types/jest": "^29.5.4",
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"@types/node": "^20.5.6",
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"babel-jest": "^29.6.4",
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"core-js": "~3.32.2",
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"eslint": "^8.49.0",
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"jest": "^29.7.0"
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},
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"dependencies": {},
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"scripts": {
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"test": "jest ./*",
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"watch": "jest --watch ./*",
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"lint": "eslint ."
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}
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}

Diff for: ‎exercises/practice/parallel-letter-frequency/parallel-letter-frequency.js

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//
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// This is only a SKELETON file for the 'Parallel Letter Frequency' exercise. It's been provided as a
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// convenience to get you started writing code faster.
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//
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export const parallelLetterFrequency = (texts) => {
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throw new Error('Remove this statement and implement this function');
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};

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