Group List by Quarters

Groups monthly financial data by calendar quarters using the getQuarter() method from the date-fns library. Each group includes individual monthly entries and an optional cumulative total for the quarter.

Useful for:

Visualizing quarterly reports
Aggregating financial or performance data
Preparing charting datasets or grouped UI views

Steps:

groupDataByQuarter(data) – Organizes data into a dictionary using keys like "2023-Q1" based on the date field.
initializeDates(groupedQuarters) – Prepares a simplified structure listing quarters and associated month strings.
initializeRestData(groupedQuarters) – Flattens the quarterly structure into tax-specific groups, returning an array of metrics (profit, profit_percent) with their per-quarter values and totals.

This modular approach is helpful when formatting data for analytics dashboards or quarterly reports.

groupDataByQuarter


import { getQuarter, parseISO } from "date-fns";
 
// data
export const TaxEntitiesKeys = {
  profit: "profit",
  profit_percent: "profit_percent",
};
 
const mockTaxes = {
  cumulative: [
    { date: "2023-01-31", profit: 1000, profit_percent: 100 },
    { date: "2023-02-28", profit: 2000, profit_percent: 200 },
    { date: "2023-04-30", profit: 3000, profit_percent: 250 },
  ],
  report: [
    { date: "2023-01-31", profit: 300, profit_percent: 30 },
    { date: "2023-02-28", profit: 500, profit_percent: 50 },
    { date: "2023-04-30", profit: 700, profit_percent: 70 },
  ],
};
// data
 
// group by quarters
const groupDataByQuarter = (data) => {
  const quarters = {};
 
  // Group data into quarters based on their date
  for (const monthData of data.report) {
    const date = parseISO(monthData.date);
    const year = date.getFullYear();
    const quarter = getQuarter(date);
    const key = `${year}-Q${quarter}`;
 
    if (!quarters[key]) {
      quarters[key] = { months: [], total: null };
    }
    quarters[key].months.push(monthData);
  }
 
  // Assign cumulative totals to their respective quarters
  for (const totalData of data.cumulative) {
    const date = parseISO(totalData.date);
    const year = date.getFullYear();
    const quarter = getQuarter(date);
    const key = `${year}-Q${quarter}`;
 
    if (quarters[key]) {
      quarters[key].total = totalData;
    }
  }
 
  return quarters;
};
 
const groupedQuarters = groupDataByQuarter(mockTaxes);
console.log(JSON.stringify({ groupedQuarters }, null, 2));
// group by quarters
 
// {
//   groupedQuarters: {
//     "2023-Q1": {
//       months: [
//         {
//           date: "2023-01-31",
//           profit: 300,
//           profit_percent: 30,
//         },
//         {
//           date: "2023-02-28",
//           profit: 500,
//           profit_percent: 50,
//         },
//       ],
//       total: {
//         date: "2023-02-28",
//         profit: 2000,
//         profit_percent: 200,
//       },
//     },
//     "2023-Q2": {
//       months: [
//         {
//           date: "2023-04-30",
//           profit: 700,
//           profit_percent: 70,
//         },
//       ],
//       total: {
//         date: "2023-04-30",
//         profit: 3000,
//         profit_percent: 250,
//       },
//     },
//   },
// };
 
// dates
const initializeDates = (quarters) => {
  const dates = [];
 
  Object.entries(quarters).forEach(([dateKey, data]) => {
    const [year, quarter] = dateKey.split("-Q").map(Number);
 
    let yearEntry = dates.find((entry) => entry.year === year);
    if (!yearEntry) {
      yearEntry = { year, periods: [] };
      dates.push(yearEntry);
    }
 
    yearEntry.periods.push({
      months: data.months.map((month) => month.date),
      quarter: `${quarter}`,
    });
  });
 
  return dates;
};
 
console.log(
  JSON.stringify({ dates: initializeDates(groupedQuarters) }, null, 2),
);
// dates
 
// {
//   dates: [
//     {
//       year: 2023,
//       periods: [
//         {
//           months: ["2023-01-31", "2023-02-28"],
//           quarter: "1",
//         },
//         {
//           months: ["2023-04-30"],
//           quarter: "2",
//         },
//       ],
//     },
//   ],
// };
 
// rest data
const initializeRestData = (quarters) => {
  return Object.keys(TaxEntitiesKeys).map((taxKey) => {
    const taxKeyTyped = taxKey;
 
    return {
      title: taxKeyTyped,
      periods: Object.entries(quarters).map(([_, data]) => ({
        months: data.months.map((month) => month[taxKeyTyped]),
        total: data.total ? data.total[taxKeyTyped] : null,
      })),
    };
  });
};
 
console.log(
  JSON.stringify({ restData: initializeRestData(groupedQuarters) }, null, 2),
);
// rest data
 
// {
//   restData: [
//     {
//       title: "profit",
//       periods: [
//         {
//           months: [300, 500],
//           total: 2000,
//         },
//         {
//           months: [700],
//           total: 3000,
//         },
//       ],
//     },
//     {
//       title: "profit_percent",
//       periods: [
//         {
//           months: [30, 50],
//           total: 200,
//         },
//         {
//           months: [70],
//           total: 250,
//         },
//       ],
//     },
//   ],
// };