如何获取数组中重复对象的数量[重复]答案

【问题标题】：How to get count of duplicate objects in Array [duplicate]如何获取数组中重复对象的数量[重复]
【发布时间】：2021-07-20 16:19:12
【问题描述】：

这是一个对象数组，我想获取数组中重复对象的计数。找出重复对象最简洁有效的方法是什么？

[
{
  partNum: 'ACDC1007',
  brandName: 'Electric',
  supplierName: 'Electric',
},
{
  partNum: 'ACDC1007',
  brandName: 'Electric',
  supplierName: 'Electric',
},
{
  partNum: 'ACDC1007',
  brandName: 'Electric',
  supplierName: 'Electric',
},
{
  partNum: 'ACDC1009',
  brandName: 'Electric',
  supplierName: 'Electric',
},

{
  partNum: 'ACDC1000',
  brandName: 'Electric',
  supplierName: 'Electric',
}

]

我正在寻找一种方法来修改基于 partNum 的对象数组，如下所示：

[
{
  partNum: 'ACDC1007',
  brandName: 'Electric',
  supplierName: 'Electric',
  count: 3
},
{
  partNum: 'ACDC1007',
  brandName: 'Electric',
  supplierName: 'Electric',
  count: 3
},
{
  partNum: 'ACDC1007',
  brandName: 'Electric',
  supplierName: 'Electric',
  count: 3
},
{
  partNum: 'ACDC1000',
  brandName: 'Electric',
  supplierName: 'Electric',
  count: 1
}
.............

] ```

Thanks

【问题讨论】：

你是否只想在所有重复对象中添加属性count。
是的，我只想在每个对象中添加 count 属性。
请添加您尝试过的代码。有很多类似的问题，例如：Javascript - Counting duplicates in object array and storing the count as a new object 和 Get duplicates in array of strings and count number of duplicates 和 Count duplicates within an Array of Objects
到目前为止你有什么尝试？

标签： javascript node.js reactjs angular typescript

【解决方案1】：

您可以使用reduce 和map 轻松实现此目的。首先统计所有对象的所有出现次数，然后动态添加属性。

const arr = [
  {
    partNum: "ACDC1007",
    brandName: "Electric",
    supplierName: "Electric",
  },
  {
    partNum: "ACDC1007",
    brandName: "Electric",
    supplierName: "Electric",
  },
  {
    partNum: "ACDC1007",
    brandName: "Electric",
    supplierName: "Electric",
  },
  {
    partNum: "ACDC1009",
    brandName: "Electric",
    supplierName: "Electric",
  },

  {
    partNum: "ACDC1000",
    brandName: "Electric",
    supplierName: "Electric",
  },
];

const countDict = arr.reduce((acc, curr) => {
  const { partNum } = curr;
  if (acc[partNum]) ++acc[partNum];
  else acc[partNum] = 1;
  return acc;
}, {});

const result = arr.map((obj) => {
  obj["count"] = countDict[obj.partNum];
  return obj;
});

console.log(result);

【讨论】：

取决于你如何处理。我的意思是你要在这个数组中改变什么？请详细说明
我能达到同样的结果吗？如果我将数组更改为此。 ? const arr = [ { produsts : { partNum: "ACDC1007", brandName: "Electric", supplierName: "Electric", }, }, { produsts : { partNum: "ACDC1007", brandName: "Electric", supplierName: "Electric ", }, }, { produsts : { partNum: "ACDC1007", brandName: "Electric", supplierName: "Electric", }, } ]
它不适用于嵌套对象。它仅适用于没有嵌套对象并且只要对象包含属性partNum
我已经改变了逻辑，它对我来说工作正常。 const countDict = arr.reduce((acc, curr) => { const { partNum } = curr.products; if (acc[partNum]) ++acc[partNum]; else acc[partNum] = 1; return acc; } , {}); const 结果 = arr.map((obj) => { obj.products["isMatched"] = countDict[obj.products.partNum]; return obj; });