按嵌套数组键对数组进行分组，结果是重复项。

Question

这是一个有点棘手的找到正确的词，所以希望展示一些代码将有所帮助。

我有以下(简化)人员和他们的部门的数组。这来自于CMS数据，它允许将一个人添加到多个部门(因此departments是一个数组)。

[
  {
    id: '12345',
    name: 'Person 1',
    jobTitle: 'Engineering director',
    departments: ['Engineering', 'Leadership']
  },
  {
    id: '54321',
    name: 'Person 2',
    jobTitle: 'Junior engineer',
    departments: ['Engineering']
  },
  {
    id: '00001',
    name: 'Person 3',
    jobTitle: 'Founder',
    departments: ['Leadership']
  },
  {
    id: '00099',
    name: 'Person 4',
    jobTitle: 'No department',
    departments: []
  }
]

我所追求的结果是获得departments的唯一值，并为每个数组创建数组，其中包含适当的用户，如下所示：

{
  'Engineering': [
    {
      id: '12345',
      name: 'Person 1',
      jobTitle: 'Engineering director',
      departments: ['Engineering', 'Leadership']
    },
    {
      id: '54321',
      name: 'Person 2',
      jobTitle: 'Junior engineer',
      departments: ['Engineering']
    }
  ],
  'Leadership': [
    {
      id: '12345',
      name: 'Person 1',
      jobTitle: 'Engineering director',
      departments: ['Engineering', 'Leadership']
    },
    {
      id: '00001',
      name: 'Person 3',
      jobTitle: 'Founder',
      departments: ['Leadership']
    }
  ]
}

我的代码中已经有了一个groupBy函数，但它并不完全满足我的要求(因为它并不期望数组作为属性值)，所以如果一个person有多个部门，我会得到一个数组，其中两个部门的名称都是串联的，但是我希望在多个数组中出现相同的person。

这是我目前的groupBy函数，但现在它分散了我的注意力，而reduce是一个我的大脑一直在挣扎的概念.！

function groupBy(objectArray, property) {
  return objectArray.reduce(function (acc, obj) {
    var key = obj[property];
    if (!acc[key]) {
      acc[key] = [];
    }
    acc[key].push(obj);
    return acc;
  }, {});
}

// which I can use like: 

const groupedPeople = Object.entries(groupBy(people, "departments"));

// and it'll return
/*

{
  'Engineering,Leadership': [
    {
      id: '12345',
      name: 'Person 1',
      jobTitle: 'Engineering director',
      departments: ['Engineering', 'Leadership']
    }
  ],
  'Engineering': [
    {
      id: '54321',
      name: 'Person 2',
      jobTitle: 'Junior engineer',
      departments: ['Engineering']
    }
  ],
  'Leadership': [
    {
      id: '00001',
      name: 'Person 3',
      jobTitle: 'Founder',
      departments: ['Leadership']
    }
  ]
}

*/

我觉得我离得很近了，但我的大脑无法投入其中！

​

const people = [{
    id: '12345',
    name: 'Person 1',
    jobTitle: 'Engineering director',
    departments: ['Engineering', 'Leadership']
  },
  {
    id: '54321',
    name: 'Person 2',
    jobTitle: 'Junior engineer',
    departments: ['Engineering']
  },
  {
    id: '00001',
    name: 'Person 3',
    jobTitle: 'Founder',
    departments: ['Leadership']
  },
  {
    id: '00099',
    name: 'Person 4',
    jobTitle: 'No department',
    departments: []
  }
]

function groupBy(objectArray, property) {
  return objectArray.reduce(function(acc, obj) {
    var key = obj[property];
    if (!acc[key]) {
      acc[key] = [];
    }
    acc[key].push(obj);
    return acc;
  }, {});
}

// which I can use like: 

const groupedPeople = Object.entries(groupBy(people, "departments"));
console.log("Grouped:", groupedPeople);

​

Answer 1

var key = obj[property];

在代码的这一行中，key变量表示deparments数组，然后将其用作acc[key]。JS是如何将数组转换成字符串作为acc对象的键的，这是通过逗号加入数组的过程。您需要的是遍历数组，而不是：

function groupBy(objectArray, property) {
  return objectArray.reduce(function (acc, obj) {
    var keys = obj[property];
    keys.forEach(key => {
      if (!acc[key]) {
        acc[key] = [];
      }
      acc[key].push(obj);
    })
    return acc;
  }, {});
}

这种更改将使其对您的用例有效，如果键不是数组，则groupBy函数将不再工作，因此谨慎使用或使其既支持字符串又支持数组。

Answer 2

我在我的解决方案中得到了一个递归错误，在将它推入两个不同的数组之前，我不得不对一个对象(JSON.parse(JSON.stringify(obj)))进行深度复制。此外，考虑到您的属性可能是数组，也可能不是数组，我将该部分规范化为：

let keys = Array.isArray(obj[property]) ? obj[property] : [obj[property]];

​

let people = [{
    id: '12345',
    name: 'Person 1',
    jobTitle: 'Engineering director',
    departments: ['Engineering', 'Leadership']
  },
  {
    id: '54321',
    name: 'Person 2',
    jobTitle: 'Junior engineer',
    departments: ['Engineering']
  },
  {
    id: '00001',
    name: 'Person 3',
    jobTitle: 'Founder',
    departments: ['Leadership']
  },
  {
    id: '00099',
    name: 'Person 4',
    jobTitle: 'No department',
    departments: []
  }
];

function groupBy(objectArray, property) {
  return objectArray.reduce((acc, obj) => {
    let keys = Array.isArray(obj[property]) ? obj[property] : [obj[property]];
    keys.forEach(k => {
      acc[k] = acc[k] || [];
      acc[k].push(JSON.parse(JSON.stringify(obj)))
    })
    return acc;
  }, {});
}

console.log(groupBy(people, "departments"));
console.log(groupBy(people, "jobTitle"));

​

Answer 3

我只更改了3行代码片段，首先将所有内容转换为数组，然后遍历该数组并创建组使代码更容易编写。您还可以检查它是否是数组，并使用if语句编写类似的代码。

​

const people = [{
    id: '12345',
    name: 'Person 1',
    jobTitle: 'Engineering director',
    departments: ['Engineering', 'Leadership']
  },
  {
    id: '54321',
    name: 'Person 2',
    jobTitle: 'Junior engineer',
    departments: ['Engineering']
  },
  {
    id: '00001',
    name: 'Person 3',
    jobTitle: 'Founder',
    departments: ['Leadership']
  },
  {
    id: '00099',
    name: 'Person 4',
    jobTitle: 'No department',
    departments: []
  }
]

function groupBy(objectArray, property) {
  return objectArray.reduce(function(acc, obj) {
    if (obj[property] === null || obj[property] === undefined) return acc; // if obj[property] is not defined or it's null don't add it to groupts
    if (obj[property].constructor !== Array) obj[property] = [obj[property]] // obj[property] is always an array now
    obj[property].forEach(key => {
      if (!acc[key]) {
        acc[key] = [];
      }
      acc[key].push(obj);
    })
    return acc;
  }, {});
}

// which I can use like: 

const groupedPeople = Object.entries(groupBy(people, "departments"));
console.log("Grouped:", groupedPeople);

​