对象数组到以属性为键的对象答案

【问题标题】：Array of objects to objects with properties as keys对象数组到以属性为键的对象
【发布时间】：2019-03-27 13:01:41
【问题描述】：

我需要一些帮助才能从对象数组中获取对象，其中的键来自初始数组中对象的嵌套属性。这是初始数组：

[  
   {  
      "id":{  
         "colName":"columnA",
         "recId":"123"
      },
      "desc":"this is a description for A",
      "resCode":"-1"
   },
   {  
      "id":{  
         "colName":"columnB",
         "recId":"123"
      },
      "desc":"this is a  description for B",
      "resCode":"-1"
   },
   {  
      "id":{  
         "colName":"columnC",
         "recId":"234"
      },
      "desc":"description for column c ",
      "resCode":"-1"
   }
];

我想要的输出是这样的：

{
    123: {
        columnA: {
            desc: "this is a description for A",
            rescode: "-1"
        }
        columnB: {
            desc: "this is a description for B",
            rescode: "-1"
        }
    },
    234: {
        columnC: {
            desc: "description for column c ",
            resCode: "-1",
        }
    }
}

我尝试使用 reduce 来执行此操作，但我遇到了问题。我不知道如何（以及何时）“清除”临时变量，所以我只能拥有属于一个 recId 的列名。

    const initialArray =  [
     {
      "id": {
        "colName": "columnA",
        "recId": "123"
      },
      "desc": "this is a description for A",
      "resCode": "-1"
    },
    {
      "id": {
        "colName": "columnB",
        "recId": "123"
      },
      "desc": "this is a  description for B",
      "resCode": "-1"
    },
    {
      "id": {
        "colName": "columnC",
        "recId": "234"
      },
      "desc": "description for column c ",
      "resCode": "-1"
    }
  ];
    let temp = {};
    const mappedObj = initialArray.reduce((obj, item) => {
      temp[item.id.colName] = Object.assign({}, {desc: item.desc}, {resCode: item.resCode} );
      obj[item.id['recId']] = Object.assign({},  temp);
      return obj;
    }, {});
    console.log(mappedObj);

【问题讨论】：

标签： javascript arrays object reduce

【解决方案1】：

你不需要在reduce之外维护一个临时变量，你可以简单地在reduce本身中处理相同的动作

const initialArray =  [
     {
      "id": {
        "colName": "columnA",
        "recId": "123"
      },
      "desc": "this is a description for A",
      "resCode": "-1"
    },
    {
      "id": {
        "colName": "columnB",
        "recId": "123"
      },
      "desc": "this is a  description for B",
      "resCode": "-1"
    },
    {
      "id": {
        "colName": "columnC",
        "recId": "234"
      },
      "desc": "description for column c ",
      "resCode": "-1"
    }
  ];
    const mappedObj = initialArray.reduce((obj, item) => {
      obj[item.id.recId] = {...(obj[item.id.recId] || {}), [item.id.colName]: {desc: item.desc, resCode: item.resCode}}
      return obj;
    }, {});
    console.log(mappedObj);

【讨论】：