Advent of Code, Day 1 Part 2

aoc1.js

const input = [-14, -9, -14, -12, 13, 2, 7] // etc

let frequencies = [0];
let winner = null;

while (!winner) {
  const inputValue = input[(frequencies.length - 1) % input.length];
  const previousFrequency = frequencies[frequencies.length - 1];
  const newFrequency = previousFrequency + inputValue;

  if (frequencies.includes(newFrequency)) {
    winner = newFrequency;
  }

  frequencies.push(newFrequency);
}

console.log(winner);