javascript - 按键对数组进行分组，并在每次迭代中创建相关键的数组

Question

给定一个对象数组

const data = [ 
  { id: 1,
    documentation_id: 4,
    document_id: 'nil',
    category_id: 1,
    created_at: "2020-03-29T11:06:44.000Z",
    updated_at: "2020-03-29T11:06:44.000Z" },
  { id: 11,
    documentation_id: 10,
    document_id: 'nil',
    category_id: 1,
    created_at: "2020-03-29T11:06:44.000Z",
    updated_at: "2020-03-29T11:06:44.000Z" },
  { id: 2,
    documentation_id: 5,
    document_id: '1',
    category_id: 2,
    created_at: "2020-03-29T11:06:44.000Z",
    updated_at: "2020-03-29T11:06:44.000Z" },
  { id: 100,
    documentation_id: 15,
    document_id: '10',
    category_id: 2,
    created_at: "2020-03-29T11:06:44.000Z",
    updated_at: "2020-03-29T11:06:44.000Z" },
  { id: 3,
    documentation_id: 5,
    document_id: '3',
    category_id: 3,
    created_at: "2020-03-29T11:06:44.000Z",
    updated_at: "2020-03-29T11:06:44.000Z" },
  { id: 4,
    documentation_id: 6,
    document_id: '1',
    category_id: 4,
    created_at: "2020-03-29T11:06:44.000Z",
    updated_at: "2020-03-29T11:06:44.000Z" },
  { id: 5,
    documentation_id: 6,
    document_id: '3',
    category_id: 5,
    created_at: "2020-03-29T11:06:44.000Z",
    updated_at: "2020-03-29T11:06:44.000Z" },
  { id: 6,
    documentation_id: 6,
    document_id: '5',
    category_id: 1,
    created_at: "2020-03-29T11:06:44.000Z",
    updated_at: "2020-03-29T11:06:44.000Z" 
  },
  { id: 7,
    documentation_id: 7,
    document_id: '1',
    category_id: 6,
    created_at: "2020-03-29T11:06:44.000Z",
    updated_at: "2020-03-29T11:06:44.000Z"}]

我希望能够按category_id进行分组，结果如下所示

const data = [{
    category_id: 1,
    documentation: [{
        document_id: "nil",
        documentation_id: 4
    }, {
        document_id: "nil",
        documentation_id: 10
    }, {
        document_id: "5",
        documentation_id: 6
    }]
}, {
    category_id: 2,
    documentation: [{
        document_id: "1",
        documentation_id: 5
    }, {
        document_id: "10",
        documentation_id: 15
    }]
}, {
    category_id: 3,
    documentation: [{
        document_id: "3",
        documentation_id: 5
    }]
}, {
    category_id: 4,
    documentation: [{
        document_id: "1",
        documentation_id: 6
    }]
}, {
    category_id: 5,
    documentation: [{
        document_id: "3",
        documentation_id: 6
    }]
}, {
    category_id: 6,
    documentation: [{
        document_id: "1",
        documentation_id: 7
    }]
}]

如果该类别多次存在，则创建一个文档数组并将该类别中的文档推送到该数组中。如果该类别存在一次，则将该类别的唯一文档推送到数组中。

这是我想出的低效解决方案。我想优化解决方案

function groupDocumentationByCategory(data) {
    const result = [];
    const formattedArray = data.slice(0);
    const seen = [];
    for (let k = 0; k < data.length; k++) {
        if (seen.indexOf(data[k].category_id) < 0) {
            seen.push(data[k].category_id);
            formattedArray[k].documentation = [];
            for (let j = 0; j < formattedArray.length; j++) {
                if (data[k].category_id === data[j].category_id) {
                    formattedArray[k].documentation.push({
                        document_id: formattedArray[j].document_id,
                        documentation_id: formattedArray[j].documentation_id,
                    });
                    delete data[k].documentation_id;
                    delete data[k].document_id;
                    delete data[k].created_at;
                    delete data[k].updated_at;
                }
            }
            result.push(data[k]);
        }
    }
    return result;
}

Answer 1

迭代数组并构造一个由category_id索引的对象。第一次找到 category_id 时，创建 id 和 category_id 属性，并将 documentation 属性初始化为空数组。然后推送到该数组。最后，获取对象的值:

const data=[{id:1,documentation_id:4,document_id:"nil",category_id:1,created_at:"2020-03-29T11:06:44.000Z",updated_at:"2020-03-29T11:06:44.000Z"},{id:11,documentation_id:10,document_id:"nil",category_id:1,created_at:"2020-03-29T11:06:44.000Z",updated_at:"2020-03-29T11:06:44.000Z"},{id:2,documentation_id:5,document_id:"1",category_id:2,created_at:"2020-03-29T11:06:44.000Z",updated_at:"2020-03-29T11:06:44.000Z"},{id:100,documentation_id:15,document_id:"10",category_id:2,created_at:"2020-03-29T11:06:44.000Z",updated_at:"2020-03-29T11:06:44.000Z"},{id:3,documentation_id:5,document_id:"3",category_id:3,created_at:"2020-03-29T11:06:44.000Z",updated_at:"2020-03-29T11:06:44.000Z"},{id:4,documentation_id:6,document_id:"1",category_id:4,created_at:"2020-03-29T11:06:44.000Z",updated_at:"2020-03-29T11:06:44.000Z"},{id:5,documentation_id:6,document_id:"3",category_id:5,created_at:"2020-03-29T11:06:44.000Z",updated_at:"2020-03-29T11:06:44.000Z"},{id:6,documentation_id:6,document_id:"5",category_id:1,created_at:"2020-03-29T11:06:44.000Z",updated_at:"2020-03-29T11:06:44.000Z"},{id:7,documentation_id:7,document_id:"1",category_id:6,created_at:"2020-03-29T11:06:44.000Z",updated_at:"2020-03-29T11:06:44.000Z"}];

const dataByCategory = {};
for (const { id, category_id, document_id, documentation_id } of data) {
  if (!dataByCategory[category_id]) {
    dataByCategory[category_id] = {
      id,
      category_id,
      documentation: []
    };
  }
  dataByCategory[category_id].documentation.push({ document_id, documentation_id });
}

console.log(Object.values(dataByCategory));