将平面的对象数组转换为嵌套的对象数组

认为这是一个有趣的小问题，所以我做了…但是，我确实同意那些问"你迄今为止尝试过什么"的人。通常，您应该谈论一个特定的问题。

// Groups a flat array into a tree. 
// "data" is the flat array.
// "keys" is an array of properties to group on.
function groupBy(data, keys) { 
    if (keys.length == 0) return data;
    // The current key to perform the grouping on:
    var key = keys[0];
    // Loop through the data and construct buckets for
    // all of the unique keys:
    var groups = {};
    for (var i = 0; i < data.length; i++)
    {
        var row = data[i];
        var groupValue = row[key];
        if (groups[groupValue] == undefined)
        {
            groups[groupValue] = new Array();
        }
        groups[groupValue].push(row);
    }
    // Remove the first element from the groups array:
    keys.reverse();
    keys.pop()
    keys.reverse();
    // If there are no more keys left, we're done:
    if (keys.length == 0) return groups;
    // Otherwise, handle further groupings:
    for (var group in groups)
    {
        groups[group] = groupBy(groups[group], keys.slice());
    }
    return groups;
}

像这样调用方法:

var groupedData = groupBy(data, ["city","description","department"]);

该方法对数据的输出如下所示:

{
    "Toronto": {
        "Programmer": {
            "Finance": [
                {
                    "id": "1", "first_name": "Jason", "last_name": "Martin", "start_date": "1996-07-25", "end_date": "2006-07-25", "salary": "1234.56", "city": "Toronto", "description": "Programmer", "department": "Finance", "active": "1"
                }
            ]
        }
    },
    "Vancouver": {
        "Tester": {
            "Finance": [
                {
                    "id": "2", "first_name": "Alison", "last_name": "Mathews", "start_date": "1976-03-21", "end_date": "1986-02-21", "salary": "6661.78", "city": "Vancouver", "description": "Tester", "department": "Finance", "active": "1"
                }
            ],
            "QA": [
                {
                    "id": "3", "first_name": "James", "last_name": "Smith", "start_date": "1978-12-12", "end_date": "1990-03-15", "salary": "6544.78", "city": "Vancouver", "description": "Tester", "department": "QA", "active": "1"
                }
            ],
            "IT": [
                {
                    "id": "5", "first_name": "Robert",  "last_name": "Black", "start_date": "1984-01-15", "end_date": "1998-08-08", "salary": "2334.78", "city": "Vancouver", "description": "Tester", "department": "IT", "active": "1"
                }
            ]
        },
        "Manager": {
            "HR": [
                {
                    "id": "4", "first_name": "Celia", "last_name": "Rice", "start_date": "1982-10-24", "end_date": "1999-04-21", "salary": "2344.78", "city": "Vancouver", "description": "Manager", "department": "HR", "active": "1"
                }
            ]
        }
    },
    "New York": {
        "Tester": {
            "QA": [
                {
                    "id": "6", "first_name": "Linda", "last_name": "Green", "start_date": "1987-07-30", "end_date": "1996-01-04", "salary": "4322.78", "city": "New York", "description": "Tester", "department": "QA", "active": "1"
                }
            ]
        },
        "Manager": {
            "HR": [
                {
                    "id": "7", "first_name": "David", "last_name": "Larry", "start_date": "1990-12-31", "end_date": "1998-02-12", "salary": "7897.78", "city": "New York", "description": "Manager", "department": "HR", "active": "1"
                }
            ]
        }
    }
}

因为组都是javascript对象，所以不需要"count"成员。您可以简单地使用数组的.length属性。

使用javascript的for (var group in groups)语法遍历组

你可以看看D3.js中的nest()操作符:https://github.com/mbostock/d3/blob/48ad44fdeef32b518c6271bb99a9aed376c1a1d6/src/arrays/nest.js这是D3的一部分，一个更大的库，但快速查看我刚刚链接到的代码，我不认为这有任何依赖关系，所以你应该能够在这里解除代码用于你自己的项目。用法在这里的文档中描述-您链接.key()方法来定义嵌套结构的每一层的键。在您的示例中，这可能看起来像:

data = d3.nest()
    .key(function(d) { return d.city })
    .key(function(d) { return d.description })
    .entries(data);

生成的结构与您的结构略有不同，但功能非常相似:

[
  {
    "key": "Toronto", 
    "values": [
      {
        "key": "Programmer", 
        "values": [
          {
            "active": "1", 
            "city": "Toronto", 
            "department": "Finance", 
            "description": "Programmer", 
            "end_date": "2006-07-25", 
            "first_name": "Jason", 
            "id": "1", 
            "last_name": "Martin", 
            "salary": "1234.56", 
            "start_date": "1996-07-25"
          },
          // etc ...
        ]
      }
    ]
  },
  // etc ...
]

以@nrabinowitz提供的示例为基础，下面是嵌套函数，使用最初提出的API，将集合和属性名称数组作为参数传递，使用d3。巢在引擎盖下:

function nest(data, keys) {
  var nest = d3.nest();
  keys.forEach(function(k) { 
    nest.key(function(d) {
      return d[k];
    })
  });
  return nest.entries(data);
}

使用https://www.npmjs.com/package/nesthydrationjs

const NestHydrationJS = require('nesthydrationjs')();
function getNestHydrationJS (results) {
  return  NestHydrationJS.nest(results);
}