advent of code 2020 day 3 part 2

day3_part2.js

const fs = require('fs')
const splitted = fs.readFileSync('./input.txt', 'utf-8').split(String.fromCharCode(0x0a))

function normalizePattern(splt) {
	let nSplt = splt
	let normLen = 90

	for (let i = 0; i < (splt.length - 1); i++) {
		nSplt[i] = splt[i].repeat(normLen)
	}

	return nSplt
}

function countTree(splt, right, down) {
	let numTree = 0, position = right

	for (let i = down; i < splt.length; i += down) {
		if (splt[i].charAt(position) == '#') {
			numTree++
		}

		position += right
	}

	return numTree
}

normalized = normalizePattern(splitted)
list = [
	countTree(normalized, 1, 1),
	countTree(normalized, 3, 1),
	countTree(normalized, 5, 1),
	countTree(normalized, 7, 1),
	countTree(normalized, 1, 2)
]

console.log(list.reduce((x, y) => x * y))