为什么当尝试循环嵌套在对象内的键时，这个 for...in 循环不起作用？

Question

我尝试循环嵌套在对象内部的前端开发人员的名称（请参阅代码），当我将其打印到控制台时，它说显示未定义。

var employees =
    {
        sales:  {
            manager: {
                name: 'Evan',
                gender: 'Male',
                age: 41,
                salary: 2000
            },
            sales_rep:  {
                name: 'Cilian',
                gender: 'Male',
                age: 24,
                slary: 1000
            },
            sales_executive:    {
                name: 'Joanna',
                gender: 'Female',
                age: 23,
                salary: 1000
            }

        },
        engineering:    {
            manager:    {
                name: 'Mike',
                gender: 'Male',
                age: 39,
                salary: 3000
            },
            designer:   {
                userExperience: {
                    name: 'Amy',
                    gender: 'Female',
                    age: 25,
                    salary: 1000
                },
                userInterface:  {
                    name: 'Jenna',
                    gender: 'Female',
                    age: 24,
                    salary: 1000
                }
            },
            developer:  {
                frontEndDeveloper:  {
                    name: 'John',
                    gender: 'Male',
                    age: 27,
                    salary: 2000
                },
                backEndDeveloper:   {
                    name: 'Felix',
                    gender: 'Male',
                    age: 28,
                    salary: 2000
                }
            }
        }
    
    }
;
var display;

for (let sector in employees) {
    display = `${sector}: ${employees.engineering.developer[sector].name}`;
}

首先，我认为显示范围在 for 循环内，因此我将显示变量移到了 for 循环之外。自从我开始学习 JavaScript 已经过去了 4 天，所以我对这些概念还很陌生。

Answer 1

您的代码中有一个小错误。 您可以直接从对象中获取 frontEndDeveloper 名称。请检查下面更新的代码。

  var employees =
    {
        sales:  {
            manager: {
                name: 'Evan',
                gender: 'Male',
                age: 41,
                salary: 2000
            },
            sales_rep:  {
                name: 'Cilian',
                gender: 'Male',
                age: 24,
                slary: 1000
            },
            sales_executive:    {
                name: 'Joanna',
                gender: 'Female',
                age: 23,
                salary: 1000
            }

        },
        engineering:    {
            manager:    {
                name: 'Mike',
                gender: 'Male',
                age: 39,
                salary: 3000
            },
            designer:   {
                userExperience: {
                    name: 'Amy',
                    gender: 'Female',
                    age: 25,
                    salary: 1000
                },
                userInterface:  {
                    name: 'Jenna',
                    gender: 'Female',
                    age: 24,
                    salary: 1000
                }
            },
            developer:  {
                frontEndDeveloper:  {
                    name: 'John',
                    gender: 'Male',
                    age: 27,
                    salary: 2000
                },
                backEndDeveloper:   {
                    name: 'Felix',
                    gender: 'Male',
                    age: 28,
                    salary: 2000
                }
            }
        }
    
    }
;
var display = employees.engineering.developer.frontEndDeveloper.name;

console.log(display);

让我知道它是否适合您。