删除对象属性不是唯一的数组项 [英] Remove array items where object property is not unique

问题描述

我有一个对象数组，我需要根据 data-itemid 道具删除重复项。

I have an array with objects and I need to remove duplicates based on the data-itemid prop.

这是我的代码：

const ListItemsUnique = []
ListItems.map(item => {
  if (ListItemsUnique.indexOf(item.props['data-itemid']) === -1) {
    ListItemsUnique.push(item)
  }
});

它返回与以前完全相同的数组，我在做什么错了？

It returns exactly the same array as before, what am I doing wrong?

推荐答案

最简单，最干净的方法是使用临时集存储在映射过程中先前返回到数组的项目。像这样：

The easiest and cleanest way would be to use a temporary set to store which items you have previously returned to your array, while you're mapping through it. Like so:

let tempSet = new Set();
const ListItemsUnique = ListItems.filter(item => {
  if(!tempSet.has(item.props['data-itemid'])) {
      tempSet.add(item.props['data-itemid']);
    return item;
  }
});

然后照常进行映射。

let ListItems = [
  {name: "A", props: {"data-itemid": 1}},
  {name: "B", props: {"data-itemid": 1}},
  {name: "C", props: {"data-itemid": 2}},
  {name: "D", props: {"data-itemid": 3}},
  {name: "E", props: {"data-itemid": 3}},
];  //mock data

let tempSet = new Set();
const ListItemsUnique = ListItems.filter(item => {
  if(!tempSet.has(item.props['data-itemid'])) {
    tempSet.add(item.props['data-itemid']);
    return item;
  }
})

console.log(ListItemsUnique.map(item => item.name));  //Items "B" and "E" are skipped

顺便说一句， Set 非常适合处理或希望获得唯一的数据集合。阅读 MDN 有关 Set 的更多信息。

By the way, Set is great for when dealing with, or wanting to achieve, a unique collection of data. Have a read on the MDN for more info on Set.

以下是文档的摘录：

Set 对象是值的集合。您可以按插入顺序遍历集合的元素。 Set 中的值只能出现一次；它在 Set 的集合中是唯一的。

Set objects are collections of values. You can iterate through the elements of a set in insertion order. A value in the Set may only occur once; it is unique in the Set's collection.

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