avg/lib/index.js

calculate rounded averages

class Averages {
  calculate(object) {
    const total = Object.keys(object).reduce(
      (sum, key) => sum + object[key],
      0
    );
    const averages = {};
    let roundedTotal = 0;

    for (let key in object) {
      const value = object[key];
      averages[key] = total === 0 ? 0 : (parseInt(value, 10) / total) * 100;
      roundedTotal += Math.round(averages[key]);
    }
    return this.round(averages, roundedTotal);
  }

  round(averages, roundedTotal) {
    const roundedAverages = {};
    const correction = 100 - roundedTotal;

    if (correction === 0 || correction === 100) {
      for (let key in averages) {
        roundedAverages[key] = Math.round(averages[key]);
      }
      return roundedAverages;
    }

    const sortedByDecimals = Object.keys(averages).sort((key) => {
      return (
        (1 / ((averages[key] % 1) - 0.5)) * (correction / Math.abs(correction))
      );
    });
    for (let i = 0; i < Object.keys(averages).length; i++) {
      if (i < Math.abs(correction)) {
        roundedAverages[sortedByDecimals[i]] = Math.round(
          (averages[sortedByDecimals[i]] +=
            (0.5 * correction) / Math.abs(correction))
        );
      } else {
        roundedAverages[sortedByDecimals[i]] = Math.round(
          averages[sortedByDecimals[i]]
        );
      }
    }
    return roundedAverages;
  }
}

module.exports = Averages;