获取对象数组中重复对象的列表 [英] Get list of duplicate objects in an array of objects

问题描述

我正在尝试获取对象数组中的重复对象.假设对象如下所示.

I am trying to get duplicate objects within an array of objects. Let's say the object is like below.

values = [
  { id: 10, name: 'someName1' },
  { id: 10, name: 'someName2' },
  { id: 11, name: 'someName3' },
  { id: 12, name: 'someName4' }
];

重复的对象应该返回如下:

Duplicate objects should return like below:

duplicate = [
  { id: 10, name: 'someName1' },
  { id: 10, name: 'someName2' }
];

推荐答案

您可以使用 Array#reduce 根据id 键制作一个计数器查找表，然后使用Array#filter 删除任何在查找表中只出现一次的项目.时间复杂度为 O(n).

You can use Array#reduce to make a counter lookup table based on the id key, then use Array#filter to remove any items that appeared only once in the lookup table. Time complexity is O(n).

const values = [{id: 10, name: 'someName1'}, {id: 10, name: 'someName2'}, {id: 11, name:'someName3'}, {id: 12, name: 'someName4'}];

const lookup = values.reduce((a, e) => {
  a[e.id] = ++a[e.id] || 0;
  return a;
}, {});

console.log(values.filter(e => lookup[e.id]));

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