使用 FlatMap/Map 为每个对象添加父属性答案

【问题标题】：Add Parent Property to each Objects using FlatMap/Map使用 FlatMap/Map 为每个对象添加父属性
【发布时间】：2023-01-15 14:47:09
【问题描述】：

我试图在几行代码中实现以下结果。

预期结果：

[{
  active: true,
  id: 1,
  name: "California",
  country: USA
}, {
  active: true,
  id: 2,
  name: "New York",
  country:"USA"
},...
 {
  active: true,
  id: 4,
  name: "Moscow",
  country:"Russia"
}, ....]

这是我尝试过的，但结果中再次缺少一个属性country。期望以最短且有效的方式实现这一目标。谢谢你的回复。

 const obj = [
    {
      country: "USA",
      cities: ["California", "New York", "Austin"]
    },
    {
      country: "Russia",
      cities: ["Moscow", "kazan", "Samara"]
    }
  ];
 
//here the map of country is not there, wondering how to achieve this.
//obj.map(y => y.country).flatMap(x => x.cities)
const aa = obj.flatMap(x => x.cities)
   .map((str, index) => ({ name: str, id: index + 1, active:true}));

console.log(aa)

【问题讨论】：

标签： javascript typescript

【解决方案1】：

提取country和cities，映射cities以创建对象并包含country：

const obj = [{"country":"USA","cities":["California","New York","Austin"]},{"country":"Russia","cities":["Moscow","kazan","Samara"]}];

const result = obj.flatMap(({ country, cities }) => 
  cities.map((str, index) => ({
    name: str,
    country,
    id: index + 1,
    active: true
  }))
);

console.log(result)

【讨论】：

【解决方案2】：

按照这种方式：

const results = obj.flatMap(({ country, cities }) => {
    return cities.map((city, index) => ({
        active: true,
        id: index + 1,
        name: city,
        country: country
    }));
});
console.log(results);

【讨论】：