JavaScript calculation pie chart values.

calcPieChartValues.js

{
  const calcPieChartValues = (values, numDegits = null) => {
    const totalValue = values.reduce((a, c) => a + c);
    const deg2rad = (deg) => deg * Math.PI / 180;

    return values.map((value, i) => {
      const data = {};
      data.index     = i;
      data.value     = value;
      data.rate      = value / totalValue;
      data.percent   = value / totalValue * 100;

      // degrees
      data.angle_deg = 360 * value / totalValue;
      data.strat_deg = values.slice(0, i).reduce((a, c) => a + 360 * c / totalValue, 0);
      data.mid_deg   = data.strat_deg + data.angle_deg / 2;
      data.end_deg   = data.strat_deg + data.angle_deg;

      // radian
      data.angle_rad = deg2rad(data.angle_deg);
      data.start_rad = deg2rad(data.strat_deg);
      data.mid_rad   = deg2rad(data.mid_deg);
      data.end_rad   = deg2rad(data.end_deg);
      
      // other info
      data.quadrant  = Math.floor(data.mid_deg / 90) + 1;

      if (typeof numDegits === "number" && numDegits >= 0) {
        tmpMultiple = 10 ** numDegits;
        for (key in data) {
          if (key === "value" || key === "quadrant") continue;
          data[key] = Math.round(data[key] * tmpMultiple) / tmpMultiple;
        }
      }
      return data;
    });
  };
  
  const testData = [10, 20, 30, 40, 50, 60, 70, 80, 90, 100];
  console.log(JSON.stringify(calcPieChartValues(testData, 4), null, 2));
}