Heard you kids still like 'em shloppy - here's day 3

advent2021_day_3.js

const data = require('./data.json');

const getFrequency = (arr) => {
    const dict = {};
    arr.forEach(function(el) {
      if (!dict[el]) dict[el] = 0;
      dict[el]++;
    });
    return {
      leastFrequent: `${Object.keys(dict).find(key => dict[key] === Math.min(...Object.values(dict)))}`,
      mode: `${Object.keys(dict).find(key => dict[key] === Math.max(...Object.values(dict)))}`,
    };
}

const results = data.data.reduce((acc, val, idx, arr) => {
  val.split('').forEach((v, i) => {
    const newSplitArr = [
      ...(acc.splitBitsArr[i] || []),
      v
    ];
    const { leastFrequent, mode } = getFrequency(newSplitArr);

    acc.splitBitsArr[i] = newSplitArr;
    acc.modeArr[i] = mode;
    acc.leastFrequentArr[i] = leastFrequent;
    acc.gammaBinary = acc.modeArr.join('');
    acc.epsilonBinary = acc.leastFrequentArr.join('');
    acc.gammaDecimal = parseInt(acc.gammaBinary, 2);
    acc.epsilonDecimal = parseInt(acc.epsilonBinary, 2);
  })

  return acc;
}, {
  epsilonBinary: "000000000000",
  gammaBinary: "000000000000",
  epsilonDecimal: 0,
  gammaDecimal: 0,
  modeArr: [],
  leastFrequentArr: [],
  splitBitsArr: [],
});

console.log(results.epsilonBinary);
console.log(results.epsilonDecimal);
console.log(results.gammaBinary);
console.log(results.gammaDecimal);
console.log(results.gammaDecimal * results.epsilonDecimal);