在对象内获取对象内的对象

var person = {
  name: "John",
  age: 30,
  address: {
    street: "123 Main St",
    city: "New York",
    country: "USA"
  }
};

var street = person.address.street; // 获取address对象内的street属性
var city = person.address.city; // 获取address对象内的city属性
var country = person.address.country; // 获取address对象内的country属性

var person = {
  name: "John",
  age: 30,
  address: {
    street: "123 Main St",
    city: "New York",
    country: "USA"
  }
};

var street = person["address"]["street"]; // 获取address对象内的street属性
var city = person["address"]["city"]; // 获取address对象内的city属性
var country = person["address"]["country"]; // 获取address对象内的country属性

var propertyName = "street";
var street = person["address"][propertyName]; // 获取address对象内的street属性