Sum percentages to 100%

oneHundredPercent.js

// Stolen from: https://revs.runtime-revolution.com/getting-100-with-rounded-percentages-273ffa70252b

export const processDatasetWithAdjustedPercentages = dataset => {
  // get the total count to caluclate the actual percentage
  const totalCount = dataset.reduce((acc, data) => acc + data.value, 0);

  // map the dataset and add properties for the percentage values we'll need
  const datasetWithPercentages = dataset.map(data => {
    const rawPercentage = (data.value / totalCount) * 100; // ex: 43.234235235
    const floorPercentage = Math.floor(rawPercentage); // ex: 43
    const decimalRemainderPercentage = rawPercentage - floorPercentage; // ex: .234235235
    return {
      ...data,
      rawPercentage,
      floorPercentage,
      decimalRemainderPercentage,
    };
  });

  // calculate the remaining percent point total value that needs to be distributed
  const remainder =
    100 -
    datasetWithPercentages.reduce((acc, data) => acc + data.floorPercentage, 0);

  // sort the dataset by the remainder decimal value
  const datasetSortedByDecimal = datasetWithPercentages.sort((a, b) => {
    if (a.decimalRemainderPercentage > b.decimalRemainderPercentage) return -1;
    if (b.decimalRemainderPercentage > a.decimalRemainderPercentage) return 1;
    return 0;
  });

  // distribute the remainder percent points
  const datasetWithAdjustedPercentages = datasetSortedByDecimal.map(
    (data, i) => {
      const adjustedPercentage =
        i < remainder ? data.floorPercentage + 1 : data.floorPercentage;
      return { ...data, adjustedPercentage };
    }
  );
  return datasetWithAdjustedPercentages;
};