Calculate investiment already discounting the tax

calculateInvestiment.js

const calculateInvestiment = (initial, months, annualInterestPercentage/*6.4 for instance*/, taxPercentage/*0 to 100*/) => {
  const monthInterestMultiplier = Math.pow((annualInterestPercentage / 100) + 1, 1 / 12) - 1;
  const totalInterestMultiplier = Math.pow(monthInterestMultiplier + 1, months) - 1;
  const total = initial * (totalInterestMultiplier + 1);
  const profit = total - initial;
  const tax = profit * taxPercentage / 100;
  const liquidProfit = profit - tax;

  return {
    initial,
    total,
    totalInterestPercentage: totalInterestMultiplier * 100,
    tax,
    taxPercentage,
    profit,
    liquidProfit,
    monthInterestPercentage: monthInterestMultiplier * 100,
  };
};