JavaScript: 如何对嵌套数组进行分组

Question

我正在尝试在 React Native 中使用 SectionList 显示数据。我已经编写了下面的代码来显示我想要完成的事情。

我希望数据首先按 date 分组在一起，然后在该日期内，我需要按位置分组。常规 JavaScript 解决方案将起作用。它有一个 title 和 data 键很重要。

我的输入数据是这种格式：

[ { game_id: 1171,
    date: '2018-11-17',
    location: 'Plaza'
   },
  { game_id: 1189,
    date: '2018-11-17',
    location: 'Field - Kickball'
   },
   { game_id: 1489,
    date: '2018-11-16',
    location: 'Field - Kickball'
   },
   { game_id: 1488,
    date: '2018-11-16',
    location: 'Field - Soccer'
   }
]

我需要从上面的数据数组中获取以下输出：

data = [{
    title: "2018-11-17",
    data: [{
            title: "Field - Kickball",
            data: [{
                game_id: 1189,
                date: '2018-11-17',
                location: 'Field - Kickball'
            }]
        },
        {
            title: "Plaza",
            data: [{
                game_id: 1171,
                date: '2018-11-17',
                location: 'Plaza'
            }]
        }
    ]
    },
    {
        title: "2018-11-16",
        data: [{
                title: "Field - Kickball",
                data: [{
                    game_id: 1489,
                    date: '2018-11-16',
                    location: 'Field - Kickball'
                }]
            },
            {
                title: "Field - Soccer",
                data: [{
                    game_id: 1488,
                    date: '2018-11-16',
                    location: 'Field - Soccer'
                }]
            }
        ]
    }
]

我已经试过了：

const games = [data here]
var groups = _(games)
.groupBy(x => x.date)
        .map(value => {
            return _.groupBy(value, 'location')
            .map(({key, value}) => ({title: key, data: value}))
        })

        .map((value, key) => {
            return ({title: value[Object.keys(value)[0]][0].date, data: value})
        })

Answer 1

你可以在没有 lodash 的情况下使用 ES6 做这样的事情：

let arr = [ { game_id: 1171, date: '2018-11-17', location: 'Plaza' }, { game_id: 1189, date: '2018-11-17', location: 'Field - Kickball' }, { game_id: 1489, date: '2018-11-16', location: 'Field - Kickball' }, { game_id: 1488, date: '2018-11-16', location: 'Field - Soccer' } ]

let groupByfield = (data, field) => data.reduce((r, c) => {
  let key = c[field]
  r[key] = r[key] || {title: key, data: []}
  r[key].data = [...(r[key].data || []), c] 
  return r
}, {})

let result = Object.values(groupByfield(arr, 'date'))
  .map(x => ({ 
    title: x.title, 
    data: Object.values(groupByfield(x.data, 'location'))
   })
)

console.log(result)

我们的想法是创建您的自定义 groupBy 函数，然后将其用于您的分组。

我们正在使用 Array.reduce, Array.map and Object.values

Answer 2

如果你想要一个标准的解决方案，那么你可以先减少到一个对象，然后 return 该对象的值，然后在输出上再次分组 :)

function groupBy( arr, prop ) {
  return Object.values( arr.reduce( ( aggregate, item ) => {
    const val = item[prop];
    if (!aggregate[val]) {
      aggregate[val] = {
        [prop]: val,
        data: []
      };
    }
    aggregate[val].data.push( item );
    return aggregate;
  }, {} ) );
}

const games = [ { game_id: 1171,
    date: '2018-11-17',
    location: 'Plaza'
   },
  { game_id: 1189,
    date: '2018-11-17',
    location: 'Field - Kickball'
   },
   { game_id: 1489,
    date: '2018-11-16',
    location: 'Field - Kickball'
   },
   { game_id: 1488,
    date: '2018-11-16',
    location: 'Field - Soccer'
   }
];

const grouped = groupBy( games, 'date' )
  .map( item => ({ ...item, data: groupBy( item.data, 'location' ) }) );
  
console.log( grouped );

请注意，我只是使用提取的道具作为目标属性进行分组，如果您想要 title，只需将 [prop]: val 更改为 'title': val 然后你可以让你的第二个分组更容易一点:)

Answer 3

有几种方法可以实现这一点，但是一种不需要第三方依赖项（如 Underscore 或 Lodash）的简单方法可以使用 built-in Array#reduce() 方法实现，如下所示。

有关此解决方案如何工作的详细信息，请参阅以下代码片段中的文档：

const input =  [ { game_id: 1171, date: '2018-11-17', location: 'Plaza' }, { game_id: 1189, date: '2018-11-17', location: 'Field - Kickball' }, { game_id: 1489, date: '2018-11-16', location: 'Field - Kickball' }, { game_id: 1488, date: '2018-11-16', location: 'Field - Soccer' } ];


/* Reduce input data to required nested sub-array structure */
const data = input.reduce((result, item) => {

  /* Construct item to be inserted into sub array for this item.date
  in resulting data object */
  const resultItem = {
    title: item.location,
    data: [{
      game_id: item.game_id,
      date: item.date,
      location: item.location
    }]
  };

  /* Find existing item in result array with title that matches date */
  const resultDateList = result.find(i => i.title === item.date);

  if (resultDateList) {

    /* If matching sublist found, add constructed item to it's data array */
    resultDateList.data.push(resultItem);
  } else {

    /* If not matching sublist found, add a new one to the result for this item
    and pre-populate the data array with new item*/
    result.push({
      title: item.date,
      data: [resultItem]
    });
  }

  return result;

}, [])

console.log(data)

希望对您有所帮助！

Answer 4

使用_.flow()生成一个函数，可以按字段对数组进行分组，并将其转换为{标题，数据}的格式。该函数还应该接受数据转换器。现在你可以递归使用它来多次分组了。

const { identity, flow, partialRight: pr, groupBy, map } = _

const groupByKey = (key, transformer = identity) => flow(
  pr(groupBy, key),
  pr(map, (data, title) => ({
    title,
    data: transformer(data)
  }))
)

const data = [{"game_id":1171,"date":"2018-11-17","location":"Plaza"},{"game_id":1189,"date":"2018-11-17","location":"Field - Kickball"},{"game_id":1489,"date":"2018-11-16","location":"Field - Kickball"},{"game_id":1488,"date":"2018-11-16","location":"Field - Soccer"}]

const result = groupByKey('date', groupByKey('location'))(data)

console.log(result)

<script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.11/lodash.js"></script>

与lodash/fp相同的想法：

const { identity, flow, groupBy, map, get } = _

const groupByKey = (key, transformer = identity) => flow(
  groupBy(key),
  map(data => ({
    title: get([0, key], data),
    data: transformer(data)
  }))
)

const data = [{"game_id":1171,"date":"2018-11-17","location":"Plaza"},{"game_id":1189,"date":"2018-11-17","location":"Field - Kickball"},{"game_id":1489,"date":"2018-11-16","location":"Field - Kickball"},{"game_id":1488,"date":"2018-11-16","location":"Field - Soccer"}]

const result = groupByKey('date', groupByKey('location'))(data)

console.log(result)

<script src='https://cdn.jsdelivr.net/g/lodash@4(lodash.min.js+lodash.fp.min.js)'></script>

JavaScript: 如何对嵌套数组进行分组

JavaScript: How to group nested array

javascript

react-native

underscore.js

lodash