docs: function computeCombinationLength(elementNumber, combinationLength) {
      elementNumber = Number(elementNumber);
      combinationLength = Number(combinationLength);
      if (!_regex.regex.positiveInteger.test(String(elementNumber))) {
          throw new Error("elementNumber should be positiveNumber but got " + elementNumber);
      }
      if (!(_regex.regex.positiveInteger.test(String(combinationLength)) || combinationLength === 0)) {
          throw new Error("elementNumber should be positiveNumber or 0 but got " + combinationLength);
      }
      if (combinationLength > elementNumber) {
          throw new Error("The max value of combinationLength should be " + elementNumber + " but got " + combinationLength);
      }
      if (combinationLength === 0) {
          return 1;
      }
      return computeFactorial(elementNumber) / (computeFactorial(combinationLength) * computeFactorial(elementNumber - combinationLength));
  }