如何按日期和值筛选对象数组

Question

我得到的是一个包含类别、日期和值的对象数组，如下所示

const records = 
  [ { category: 'Cat 1', date: '2020-11-03', value: '300.00' } 
  , { category: 'Cat 2', date: '2020-11-03', value: '350.00' } 
  , { category: 'Cat 3', date: '2020-11-03', value:  '50.00' } 
  , { category: 'Cat 1', date: '2020-11-13', value: '200.00' } 
  , { category: 'Cat 1', date: '2020-12-23', value: '100.00' } 
  , { category: 'Cat 2', date: '2020-11-23', value: '350.00' } 
  , { category: 'Cat 3', date: '2020-11-15', value:  '50.00' } 
  , { category: 'Cat 3', date: '2021-01-15', value:  '50.00' } 
  ]

我想得到的是包含每个类别、月份和每月总价值的新数组，如下所示：

const newRecords = 
  [ { category: 'Cat 1'
    , totalPerMonth: 
      [ { month: '2020-11', totalMonthlyValue: '500.00' } 
      , { month: '2020-12', totalMonthlyValue: '100.00' } 
    ] } 
  , { category: 'Cat 2'
    , totalPerMonth: 
      [ { month: '2020-11', totalMonthlyValue: '700.00' } 
    ] } 
  , { category: 'Cat 3'
    , totalPerMonth: 
      [ { month: '2020-11', totalMonthlyValue: '100.00' } 
      , { month: '2021-01', totalMonthlyValue:  '50.00' } 
  ] } ]

Answer 1

您可以先按类别将数据分组，然后再按日期分组。然后，您需要对所有值进行求和，并像定义的那样返回结构。这里有一个例子，它正是这样做的。

​

const records = [
  {category: 'Cat 1', date: '2020-11-03', value: '300.00'},
  {category: 'Cat 2', date: '2020-11-03', value: '350.00'},
  {category: 'Cat 3', date: '2020-11-03', value: '50.00'},
  {category: 'Cat 1', date: '2020-11-13', value: '200.00'},
  {category: 'Cat 1', date: '2020-12-23', value: '100.00'},
  {category: 'Cat 2', date: '2020-11-23', value: '350.00'},
  {category: 'Cat 3', date: '2020-11-15', value: '50.00'},
  {category: 'Cat 3', date: '2021-01-15', value: '50.00'}
];

// first you need to group it by category, you can do that by
// assigning a group indicator as key to an object and add an
// array as value containing all values. you can also use lodash's
// groupBy for grouping values.
const groupedRecords = {};
records.forEach(record => {
  if (groupedRecords[record.category] === undefined) {
    groupedRecords[record.category] = [];
  }
  groupedRecords[record.category].push(record);
});

// then, you need to go through each category group and group all
// records again by date. you can use the same pattern as above.
const result = Object.entries(groupedRecords).map(([category, recordsOfOneCategory]) => {
  const groupedDates = {};
  recordsOfOneCategory.forEach(record => {
    // this regex extracts the date per month. it's probably better 
    // to use a date library for this part
    const month = record.date.match(/^(\d{4}-\d{2})/)[1];
    if (groupedDates[month] === undefined) {
      groupedDates[month] = [];
    }
    groupedDates[month].push(record);
  });
  
  // now you have for each category group a group of dates with
  // records in it. you now need to make a sum for each group of
  // dates. you can do this by mapping the values into an array of
  // only values and then sum them up using reduce.
  const totalPerMonth = Object.entries(groupedDates).map(([month, items]) => ({
    month,
    totalMonthlyValue: items.map(item => parseFloat(item.value)).reduce((a,b) => a + b).toFixed(2)
  }));
  
  return { category, totalPerMonth };
});

console.log(result);

​

Answer 2

这边请

​

const records = 
  [ { category: 'Cat 1', date: '2020-11-03', value: '300.00' } 
  , { category: 'Cat 2', date: '2020-11-03', value: '350.00' } 
  , { category: 'Cat 3', date: '2020-11-03', value:  '50.00' } 
  , { category: 'Cat 1', date: '2020-11-13', value: '200.00' } 
  , { category: 'Cat 1', date: '2020-12-23', value: '100.00' } 
  , { category: 'Cat 2', date: '2020-11-23', value: '350.00' } 
  , { category: 'Cat 3', date: '2020-11-15', value:  '50.00' } 
  , { category: 'Cat 3', date: '2021-01-15', value:  '50.00' } 
  ]

const result =
  Object.values(
  records.reduce((r,{category,date,value}) =>
    {
    let Ym  = date.substring(0,7)
    if (!r[category])          r[category] = { category, sum : {} }
    if (!r[category].sum[Ym])  r[category].sum[Ym] = 0
    r[category].sum[Ym] += Number(value)
    return r
    },{}
  )).map(({category,sum}) =>
    {
    let totalPerMonth = Object.entries(sum).map(([month,sum])=>({month,totalMonthlyValue:sum.toFixed(2)}))
    return { category,totalPerMonth }
    },{})

console.log ( result  )

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​

Answer 3

可以使用对象中的array#reduce根据类别和月份进行分组。然后使用Object.values()和array#map从该对象提取所有值。

​

const records = [ { category: 'Cat 1', date: '2020-11-03', value: '300.00' } , { category: 'Cat 2', date: '2020-11-03', value: '350.00' } , { category: 'Cat 3', date: '2020-11-03', value: '50.00' } , { category: 'Cat 1', date: '2020-11-13', value: '200.00' } , { category: 'Cat 1', date: '2020-12-23', value: '100.00' } , { category: 'Cat 2', date: '2020-11-23', value: '350.00' } , { category: 'Cat 3', date: '2020-11-15', value: '50.00' } , { category: 'Cat 3', date: '2021-01-15', value: '50.00' } ],
      result = records.reduce((r, {category, date, value}) => {
        const month = date.substring(0, 7);
        r[category] ??= {category};
        r[category][month] ??= {month, total: 0};
        r[category][month].total += +value;
        return r;
      },{}),
      newRecords = Object
        .values(result)
        .map( ({category, ...rest}) => 
          ({  category, 
              totalPerMonth: Object.values(rest).map(({ month, total }) => 
                              ({ month, totalMonthlyValue: total.toFixed(2) }) 
                              ) }) );
console.log(newRecords);

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​