excel的IRR函数

office官网找到IRR的介绍

https://support.office.com/zh-cn/article/irr-%E5%87%BD%E6%95%B0-64925eaa-9988-495b-b290-3ad0c163c1bc

https://docs.microsoft.com/zh-cn/office/vba/language/reference/user-interface-help/irr-function?f1url=https%3A%2F%2Fmsdn.microsoft.com%2Fquery%2Fdev11.query%3FappId%3DDev11IDEF1%26l%3Dzh-CN%26k%3Dk(vblr6.chm1009282)%3Bk(TargetFrameworkMoniker-Office.Version%3Dv15)%26rd%3Dtrue

1.找js的实现

function IRR(cashFlows, estimatedResult) {
  var result = "isNAN";
  if (cashFlows != null && cashFlows.length > 0) {
      // check if business startup costs is not zero:
      if (cashFlows[0] != 0) {
          var noOfCashFlows = cashFlows.length;
          var sumCashFlows = 0;
          // check if at least 1 positive and 1 negative cash flow exists:
          var noOfNegativeCashFlows = 0;
          var noOfPositiveCashFlows = 0;
          for (var i = 0; i < noOfCashFlows; i++) {
              sumCashFlows += cashFlows[i];
              if (cashFlows[i] > 0) {
                  noOfPositiveCashFlows++;
              } else {
                  if (cashFlows[i] < 0) {
                      noOfNegativeCashFlows++;
                  }
              }
          }  

          // at least 1 negative and 1 positive cash flow available?
          if (noOfNegativeCashFlows > 0 && noOfPositiveCashFlows > 0) {
              // set estimated result:
              var irrGuess = 0.1; // default: 10%
              if (!isNaN(estimatedResult)) {
                  irrGuess = estimatedResult;
                  if (irrGuess <= 0) {
                      irrGuess = 0.5;
                  }
              }  

              // initialize first IRR with estimated result:
              var irr = 0;
              if (sumCashFlows < 0) { // sum of cash flows negative?
                  irr = -irrGuess;
              } else { // sum of cash flows not negative
                  irr = irrGuess;
              }  

              // iteration:
              // the smaller the distance, the smaller the interpolation
              // error
              var minDistance = 1e-15;  

              // business startup costs
              var cashFlowStart = cashFlows[0];
              var maxIteration = 100;
              var wasHi = false;
              var cashValue = 0;
              for (var i = 0; i <= maxIteration; i++) {
                  // calculate cash value with current irr:
                  cashValue = cashFlowStart; // init with startup costs  

                  // for each cash flow
                  for (var j = 1; j < noOfCashFlows; j++) {
                      cashValue += cashFlows[j] / Math.pow(1 + irr, j);
                  }  

                  // cash value is nearly zero
                  if (Math.abs(cashValue) < 0.01) {
                      result = irr;
                      break;
                  }  

                  // adjust irr for next iteration:
                  // cash value > 0 => next irr > current irr
                  if (cashValue > 0) {
                      if (wasHi) {
                          irrGuess /= 2;
                      }
                      irr += irrGuess;
                      if (wasHi) {
                          irrGuess -= minDistance;
                          wasHi = false;
                      }
                  } else {// cash value < 0 => next irr < current irr
                      irrGuess /= 2;
                      irr -= irrGuess;
                      wasHi = true;
                  }  

                  // estimated result too small to continue => end
                  // calculation
                  if (irrGuess <= minDistance) {
                      result = irr;
                      break;
                  }
              }
          }
      }
  }
  return result;
}  

2. var一个 [] 来验证找到的函数 是否可用

3.调用IRR，estimatedResult设置为0.1，保持与excel默认值一致