Advent of Code - Day 3: Perfectly Spherical Houses in a Vacuum

aoc3.js

const parseSantaRoute = (str, roboMode = false) => {
  const charFns = {
    '^': (x, y) => [x    , y + 1],
    'v': (x, y) => [x    , y - 1],
    '>': (x, y) => [x + 1, y    ],
    '<': (x, y) => [x - 1, y    ]
  };
  
  let error;
  let position = [0, 0];
  let roboPosition = [0, 0];
  let santasMove = true;
  let visitedHouses = new Map();
  visitedHouses.set(position.toString(), true);
  for (let i = 0; i < str.length; i++) {
    const char = str[i];
    const fn = charFns[char];
    if (!fn) {
      error = `Invalid character ${char} at position ${i + 1}`;
      break;
    }
    
    let newPosition;
    if (!roboMode || santasMove) {
      santasMove = false;
      newPosition = position = fn(...position);
    } else {
      santasMove = true;
      newPosition = roboPosition = fn(...roboPosition);
    }
    visitedHouses.set(newPosition.toString(), true);

  }
  return error ? {error} : {visitedHouses: visitedHouses.size};
};

const expect = (actual, expected) => {
  if (actual !== expected) {
    console.error(`Expected ${expected} got ${actual}`);
    return false;
  }
  return true;
}

console.clear()

const tests = [
  ...[
  	['>', 2],
    ['^>v<', 4]
  ].map(([str, expected]) => {
    return expect(parseSantaRoute(str).visitedHouses, expected);
  }),
  ...[
    ['^v', 3],
    ['^>v<', 3],
    ['^v^v^v^v^v', 11]
  ].map(([str, expected]) => {
    return expect(parseSantaRoute(str, true).visitedHouses, expected);
  })
];

if (tests.every(Boolean)) console.log('All tests passed!');