ℹ️ For detailed information about the contest, check out devadvent/readme

Dev Advent Calendar 🎅 Puzzle 10 - Train maintenance 🚂

Winters at the North Pole can be harsh, which not only affects the elves, but also technology. Some of the train wagons that are used to transport materials, presents, etc. in and out of the North Pole are really old. In this harsh weather, faulty brakes can cause accidents on the tracks.

That is why you're helping the head mechanic elf to check whether today's train wagons are up to code or not.

Today's puzzle is a bit more complicated. But I can give you a hint to the prize 🏆:

You need a special kind of wallet to receive it 👀

🧩 The puzzle

The concept that is being treated today is called a Singly Linked List. If this is new to you, you might get through this puzzle faster if you read up on it.

The train is composed of:

• Locomotive which is attached to a wagon
• Multiple wagons which each have a maximum of 1 wagon attached to it

The next wagon that is attached to either the locomotive or another wagon, is called next. When that value is null, that means it's the last wagon on the train.

  +-----+--+         +-----+--+          +-----+--+        +-----+------+
  |  L  |next --->   | W-1 |next --->    | W-2 |next --->  | W-3 | null |
  +-----+--+         +-----+--+          +-----+--+        +-----+------+

The box named L is the locomotive, and W-1 - W-3 are the wagons. In order to check all the wagons, you need to start at the locomotive! You can find the complete train in src/data/train.js.

💡 Hint: Check out the src/index.js file to see how the functions going to be used.

It is your job to complete two functions in the src/utils/train.js:

• iterateWagons
• filterOldBrakes

iterateWagons

"Walk" through the entire train, when given a starting point (the locomotive). There are three parameters:

• start: Starting point of the chain. Ideally the locomotive.
• actionFn: A function that is executed for every filtered item. Use the predefined defaultActionFn as default
• filterFn: Function that filters the list, following the principles of Array filter methods. Use the predefined defaultFilterFn as default

filterOldBrakes

Check if the lastBrakeRevision is older than 1 year, compared to today's date. Return true when the brake revision is older than 1 year!

ℹ️ This is a function that can be passed as filterFn in iterateWagons.

🚢 Ship your solution

Check out the contributing guide for details about how to participate.

In short:

• ✨ Create your repository by acceping the assignment using the participation link
• 🧩 Solve the puzzle
• 🐦 Add your Twitter handle to twitter.js
• 🤖 Test your solution
• 🚀 Upload your changes to the main branch

🔗 Participation link

In order to participate, you need to enter the following link and accept the assignment: https://classroom.github.com/a/4Bq3WTvV

💻 Use this project

⏳ Install the dependencies

Install the dependencies with

yarn install

or

npm install

⚙️ Run the code

Run the code with

yarn dev

or

npm run dev

🤖 Test your solution

This puzzle is equipped with automated tests (in the ./tests folder). In order for your solution to qualify for winning the daily prize, all tests need to pass.

To run these tests, execute one of the following commands in your console:

yarn test

or

npm test