JavaScript对象内函数处理问题：accountBalance返回NaN排查

核心问题 #

你的代码里模板字符串的反斜杠转义是错误的，在accountInfo和accountSummary方法中，你用了\``来包裹模板字符串，这会导致JavaScript无法正确解析模板字符串，进而在计算this.totalIncome() - this.totalExpense()`时出现异常，返回NaN。

修正后的代码 #

const personAccount = {
    firstName: 'Prashant',
    lastName: 'Singh',
    incomes: [20000, 30000, 40000],
    expenses: [],
    totalIncome: function() {
        return this.incomes.reduce((acc, curr) => acc + curr, 0);
    },
    totalExpense: function() {
        return this.expenses.reduce((acc, curr) => acc + curr, 0);
    },
    accountInfo: function () {
        return `First Name: ${this.firstName}, Last Name: ${this.lastName}, Total Income: ${this.totalIncome()}, Total Expense: ${this.totalExpense()}, Account Balance: ${this.totalIncome() - this.totalExpense()}`;
    },
    addIncome: function (income) {
        this.incomes.push(income);
        return this.incomes;
    },
    addExpense: function (expense){
        this.expenses.push(expense);
        return this.expenses;
    },
    accountBalance: function () {
        return this.totalIncome() - this.totalExpense();
    },
    accountSummary: function () {
        return `First Name: ${this.firstName}, Last Name: ${this.lastName}, Balance: ${this.accountBalance()}`;
    }
};

关键修正点 #

• 移除accountInfo和accountSummary方法中模板字符串的反斜杠\，直接使用``包裹字符串内容，让JavaScript能正确解析插值表达式。
• 可选优化：把addExpense的参数名从expenses改为expense，和对象的expenses数组名区分开，避免语义混淆。

测试验证 #

调用方法测试效果：

console.log(personAccount.accountBalance()); // 输出90000
console.log(personAccount.accountSummary()); // 输出"First Name: Prashant, Last Name: Singh, Balance: 90000"
personAccount.addExpense(15000);
console.log(personAccount.accountBalance()); // 输出75000

内容的提问来源于stack exchange，提问作者Prashant Singh