函数 sum 无法正常工作 javascript [重复]

当我添加两个字段时，代码不会对其进行求和，而是添加我输入的内容，这是我的代码

function calculate_loan() {
  var amountBorrowed = document.form.amountBorrowed.value;
  var interest = document.form.interest.value / 100;
  var payments = document.form.durationOfPayment.value;
  var monthInterest = document.form.interestPerMonth.value;
  var totalInt = document.form.totalinterest.value;


 var monthly = amountBorrowed * interest;
 var totalinterest = monthly * payments;
 var totalAmount = amountBorrowed + totalinterest;


  if (!isNaN(monthly) &&
    (monthly != Number.POSITIVE_INFINITY) &&
    (monthly != Number.NEGATIVE_INFINITY)) {


    document.form.total.value = round(totalAmount);
    document.form.totalinterest.value =
      round(monthly * payments);
          document.form.interestPerMonth.value =
      round(monthly);
  }

  else {
    document.form.amountOfPayement.value = "";
    document.form.total.value = "";
    document.form.totalinterest.value = "";
  }
}

function round(x) {
  return Math.round(x * 100) / 100;
}

例如每月利息是：720 总利息：2160 借款金额：12000 结果是 120002160。我希望结果是 14,160 请帮忙谢谢

您应该将值解析为数字

var amountBorrowed = Number(document.form.amountBorrowed.value);
var interest = Number(document.form.interest.value) / 100;
var payments = Number(document.form.durationOfPayment.value);
var monthInterest = Number(document.form.interestPerMonth.value);
var totalInt = Number(document.form.totalinterest.value);