JavaScript中如何正确传入对象属性作为函数参数解决NaN问题？

1. 对象初始化时的属性引用问题：在定义instance1对象字面量时，直接调用calculateAmount(instance1.loanAmount, ...)，此时对象还未完成初始化，instance1的属性值还未被赋值，传入函数的都是undefined，最终导致计算结果为NaN。
2. 语法与拼写错误：代码里的var sum =+ monthlyPayment * totalMonth是错误写法（=+应为=），同时montlyInterest存在拼写错误（正确应为monthlyInterest）。

方案一：先创建对象，再计算赋值 #

这种方式简单直接，确保对象属性都已初始化后再调用计算函数：

var info = [];

// 先创建完整的基础对象
var instance1 = {
    Id: 0,
    customerName: "Khawaja Sardar",
    phoneNumber: "745-544-7777",
    address: "New York, NY",
    loanAmount: 5000,
    interest: 6.0,
    loanTermYears: 5,
    loanType: "APR",
    description: "Loan domain for instance1"
};

// 对象初始化完成后，调用函数计算并赋值
instance1.calculatedLoanAmount = calculateAmount(instance1.loanAmount, instance1.interest, instance1.loanTermYears);

function calculateAmount(loanAmount, interest, loanTermYears) {
    var totalMonth = loanTermYears * 12;
    var monthlyInterest = interest / 100 / 12; // 修正拼写错误
    var temp = Math.pow(1 + monthlyInterest, totalMonth);
    var monthlyPayment = loanAmount * monthlyInterest * temp / (temp - 1);
    return monthlyPayment * totalMonth; // 直接返回总额，简化代码
}

info.push(instance1);
console.log(info);

方案二：使用Getter属性（动态计算） #

如果后续可能修改loanAmount等属性，用Getter可以实现访问calculatedLoanAmount时自动重新计算：

var info = [];

var instance1 = {
    Id: 0,
    customerName: "Khawaja Sardar",
    phoneNumber: "745-544-7777",
    address: "New York, NY",
    loanAmount: 5000,
    interest: 6.0,
    loanTermYears: 5,
    loanType: "APR",
    description: "Loan domain for instance1",
    // 定义Getter属性，访问时自动计算
    get calculatedLoanAmount() {
        var totalMonth = this.loanTermYears * 12;
        var monthlyInterest = this.interest / 100 / 12;
        var temp = Math.pow(1 + monthlyInterest, totalMonth);
        var monthlyPayment = this.loanAmount * monthlyInterest * temp / (temp - 1);
        return monthlyPayment * totalMonth;
    }
};

info.push(instance1);
console.log(info);

// 示例：修改属性后自动重新计算
instance1.loanAmount = 6000;
console.log(instance1.calculatedLoanAmount);

内容的提问来源于stack exchange，提问作者Raamis