🎄 Advent of Code 2020 | Extreme JS Edition 🎄

This is an attempt to complete all challenges for 2020's Advent of Code using pure, functional JavaScript, with the following central limitation:

Arrow functions with single-line bodies only, i.e. no function blocks / return statements allowed

The main problem with this approach is that code will generally be less readable than if I was allowed to use multi-line features such as variable declaration, object/array destructuring, if/switch statements, etc. However, I decided to gift myself an early christmas present of being hard on myself for no good reason.

The benefits of this approach are:

• While being less readable in one sense, with proper Prettier formatting, chained functions demonstrate their inherent readability and brevity
• Most of the AoC20 challenges are line-by-line array parsing — meaning I get to leverage, and learn more about, JS's array methods
• I have to be more inventive by prohibiting the use of array method function-blocks...

Some examples:

Using .reduce() to get a total

// Usually:
// { ...
const figure1 = 1000;
const figure2 = 1020;
return figure1 + figure2;

// With reduce:
// =>
[1000, 1020].reduce((total, figure) => total + figure, 0);

Carrying-over a parent array

// Usually:
// { ...
const intermediateArray = [1, 2, 3];
return intermediateArray.find(
  (figure, index) => figure + intermediateArray[index + 1] === 5
);

// Carrying-over:
// =>
[1, 2, 3].find((figure, index, numbers) => figure + numbers[index + 1] === 5);