JavaScript中如何获取对象内函数的私有变量totalSalary的取值

你代码中的totalSalary是finalSalary函数内部的局部变量，作用域仅局限于函数内部，函数执行完成后该变量就会被JS引擎回收，因此无法直接在函数外部访问该变量。

推荐解决方案：修改返回值结构 #

把finalSalary的返回值从单一的sellsBonus改为包含多个需要字段的对象，调用时即可按需取对应值：

const info = {
    firstName: "Richard",
    lastName: "Benson",
    mainSalary: 250000,
    monthlySell: 1000000,

    finalSalary: function(bonusParcent) {
        const sellsBonus = this.monthlySell * bonusParcent;
        const totalSalary = this.mainSalary + sellsBonus;
        // 返回包含两个属性的对象
        return {
            sellsBonus,
            totalSalary
        };
    }
}

console.log("Full name: " + info.firstName + " " + info.lastName);
console.log("Main salary: $", info.mainSalary);
const salaryRes = info.finalSalary(0.05);
console.log("Sells bonus: $", salaryRes.sellsBonus);
console.log("Total salary: $", salaryRes.totalSalary);

其他可选方案：挂载为对象属性 #

如果你不想修改原有返回值结构，可以把totalSalary挂载为info对象的属性，调用后直接从对象上取值：

const info = {
    firstName: "Richard",
    lastName: "Benson",
    mainSalary: 250000,
    monthlySell: 1000000,

    finalSalary: function(bonusParcent) {
        const sellsBonus = this.monthlySell * bonusParcent;
        // 将totalSalary挂载到当前对象上
        this.totalSalary = this.mainSalary + sellsBonus;
        return sellsBonus;
    }
}

console.log("Full name: " + info.firstName + " " + info.lastName);
console.log("Main salary: $", info.mainSalary);
console.log("Sells bonus: $", info.finalSalary(0.05));
console.log("Total salary: $", info.totalSalary);

注意：该方案会给info对象新增额外属性，多次调用finalSalary传入不同提成比例时，totalSalary的值会被最新的调用结果覆盖。

内容的提问来源于stack exchange，提问作者user13899130