通过存款每月复利答案

【问题标题】：Compounding interest monthly with a deposit通过存款每月复利
【发布时间】：2019-08-25 01:29:48
【问题描述】：

我想每周/每两周/每月/每年复利一次。

我还想要一个可以添加存款金额的选项。

我已经尝试过计算最终应计金额的标准公式，如下所示：

例如，这是我计算每周复利的方法：

function calculateWeekly(state: any) {
  const { savings, deposit ,interest, timePeriodSelector, timePeriodLength } = state;

  let numberOfYears = 0;

  if (timePeriodSelector === "weekly") {
    numberOfYears = timePeriodLength / weeksInAYear;
  } else if (timePeriodSelector === "fortnightly") {
    numberOfYears = (timePeriodLength / weeksInAYear) * 2;
  } else if (timePeriodSelector === "monthly") {
    numberOfYears = (timePeriodLength / weeksInAYear) * weeksInAMonth;
  } else if (timePeriodSelector === "annually") {
    numberOfYears = (timePeriodLength / weeksInAYear) * weeksInAYear;
  }

  const weeklyRate = interest / 100 / weeksInAYear;
  const lengthOfCompunding = numberOfYears * weeksInAYear;

  let startingFigure = parseInt(savings) + parseInt(deposit);

  //total gets added on for every time cycle of week
  let total =
    (startingFigure * (Math.pow(1 + weeklyRate, lengthOfCompunding) - 1)) / weeklyRate;

  return roundToTwoDP(total);
}

上述代码的问题是，每次产生利息时，存款都会被添加到计算中。因此，为期 10 周的每周 10 美元的押金实际上将加起来为 100 美元。

我在这里尝试了一种每周使用循环来累积利息的方法：

  // loops how many times to compound the interest
  for(let i = numberOfYears - (1/weeksInAYear); i > 0; i-= (1/weeksInAYear)){
    let interestGained = (total * (Math.pow((1 + weeklyRate), lengthOfCompunding))) - total;
    total += interestGained + savings;
  }

感谢您的帮助！

【问题讨论】：

总计 += 获得的利息 + 储蓄；为什么每次都增加储蓄？

标签： javascript formula

【解决方案1】：

这应该做你想做的：

const range = (min, max) => {

    const size = 1 + max - min

    return [...Array(size).keys()].map(n => n + min)
}

const weeksInAYear = 52

const addWeeklyInterest = interestRatePerWeek => (savings, _) => savings + savings * interestRatePerWeek

const calculateTotal = (savings, numberOfYears, interestRatePerWeek) => {

    const numberOfWeeks = numberOfYears * weeksInAYear

    return range(1, numberOfWeeks).reduce(addWeeklyInterest(interestRatePerWeek), savings)
}

console.log(calculateTotal(1000.00, 1, 0.02))

输出为2800.328185448178。您可能希望将其四舍五入以进行显示，但请记住，如果准确性很重要，则不能使用浮点数。

【讨论】：