AdventOfCode/JS/day2/solution_a.mjs

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JavaScript
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import * as fs from "fs";
const ENTRY_REGEX = /^(\d+?)-(\d+?) (\w?): (\w+)$/;
/**
* Main function for Puzzle A
*
* @param {string} data Puzzle input as a single string.
* @returns {number} Amount of valid passwords in puzzle input.
*/
async function main(data) {
const lines = data.split("\n").map((line) => line.trim());
const pass_data = lines.map((line) => line.match(ENTRY_REGEX));
let valid_passwords = [];
for (const entry of pass_data) {
if (!entry) throw new Error(`Failed to parse some data. ${entry}`);
const min = parseInt(entry[1]);
const max = parseInt(entry[2]);
const char = entry[3];
const pass = entry[4];
if (
pass.split(char).length - 1 >= min &&
pass.split(char).length - 1 <= max
) {
valid_passwords.push(entry);
}
}
return valid_passwords.length;
}
fs.readFile("input", (err, data) => {
if (err) throw err;
main(data.toString()).then(console.log).catch(console.error);
});