如何使用 lodash 中的 _.union 对打字稿中的多个数组进行重复数据删除？答案

【问题标题】：How to use _.union from lodash to de-duplicate multiple array in typescript?如何使用 lodash 中的 _.union 对打字稿中的多个数组进行重复数据删除？
【发布时间】：2021-08-20 02:53:14
【问题描述】：

我试过import _ from 'lodash-es' 和_.union(user.users.map(user => user.city))。但它并没有达到我的预期：["city_id1", "city_id2", "city_id3", "city_id4"]

什么是使用_.union 的正确方法，或其他更好的方法来展平所有数组并制作一个独特的数组？

### data
const user =
{
  "users": [
    {
      "id": "user_id1",
      "city": ["city_id1", "city_id2"]
    },
    {
      "id": "user_id2",
      "city": ["city_id3", "city_id4"]
    },
    {
      "id": "user_id3",
      "city": ["city_id1", "city_id3"]
    },
    {
      "id": "user_id4",
      "city": ["city_id2", "city_id4"]
    }
   ]
}

【问题讨论】：

您可以简单地使用Set 和flatMap 那么为什么在这里使用lodash？
哦，我正在学习 angular/typescript 并且不熟悉所有技巧。如果可行，我很想得到你的回答。您介意提供您的示例代码吗？谢谢

标签： javascript angular typescript lodash

【解决方案1】：

您可以使用Set 和flatMap 来获得想要的结果。

这是单线解决方案

const result = [...new Set(user.users.flatMap((o) => o.city))];
console.log(result);

const user = {
  users: [{
      id: "user_id1",
      city: ["city_id1", "city_id2"],
    },
    {
      id: "user_id2",
      city: ["city_id3", "city_id4"],
    },
    {
      id: "user_id3",
      city: ["city_id1", "city_id3"],
    },
    {
      id: "user_id4",
      city: ["city_id2", "city_id4"],
    },
  ],
};

const set = new Set(user.users.flatMap((o) => o.city));
const arr = [...set];
console.log(arr);

【讨论】：

【解决方案2】：

如果你还想使用 lodash

这就是答案


const user =
{
  "users": [
    {
      "id": "user_id1",
      "city": ["city_id1", "city_id2"]
    },
    {
      "id": "user_id2",
      "city": ["city_id3", "city_id4"]
    },
    {
      "id": "user_id3",
      "city": ["city_id1", "city_id3"]
    },
    {
      "id": "user_id4",
      "city": ["city_id2", "city_id4"]
    }
   ]
}

let a = user.users.map(item=>item.city)
_.union(...a)

【讨论】：

【解决方案3】：

遍历users数组并用_.union的结果填充另一个数组unique_cities

var user_data =
{
  "users": [
    {
      "id": "user_id1",
      "city": ["city_id1", "city_id2"]
    },
    {
      "id": "user_id2",
      "city": ["city_id3", "city_id4"]
    },
    {
      "id": "user_id3",
      "city": ["city_id1", "city_id3"]
    },
    {
      "id": "user_id4",
      "city": ["city_id2", "city_id4"]
    }
   ]
};

var unique_cities = [];
user_data.users.forEach(user => {
  unique_cities = _.union(user.city, unique_cities);
});

console.log(JSON.stringify(unique_cities.sort()));

&lt;script src="https://cdn.jsdelivr.net/npm/lodash@4.17.21/lodash.min.js"&gt;&lt;/script&gt;

【讨论】：