ES6数组中按对象属性求和

Question

我试图按日期求和单位值，并创建一个没有重复日期的新数组。 例如，我要计算2015-12-04 00:01:00的总数。 在以下数据中，该日期发生了2次，其值为5和6 ，它将是：

[{date: '2015-12-04 00:01:00', unit: 11}, ... etc]

我试过了arr = results.map(x => x.unit).reduce((a,c) => a + c)但它只返回一个值，而不是数组。

 results = [ { unit: 5, date: '2015-12-04 00:01:00' }, { unit: 10, date: '2015-12-04 00:01:00' }, { unit: 5, date: '2015-12-04 00:31:00' }, { unit: 9, date: '2015-12-04 00:31:00' }, { unit: 5, date: '2015-12-04 01:01:00' }, { unit: 10, date: '2015-12-04 01:01:00' }, { unit: 10, date: '2015-12-04 01:31:00' }, { unit: 5, date: '2015-12-04 01:31:00' }, { unit: 10, date: '2015-12-04 02:01:00' }, { unit: 5, date: '2015-12-04 02:01:00' }, { unit: 5, date: '2015-12-04 02:31:00' }, { unit: 9, date: '2015-12-04 02:31:00' }, { unit: 5, date: '2015-12-04 03:01:00' }, { unit: 9, date: '2015-12-04 03:01:00' }, { unit: 5, date: '2015-12-04 03:31:00' }, { unit: 10, date: '2015-12-04 03:31:00' }, { unit: 10, date: '2015-12-04 04:01:00' }, { unit: 5, date: '2015-12-04 04:01:00' }]; arr = results.map(x => x.unit).reduce((a,c) => a + c); console.log(arr); 

Answer 1

您可以将数据简化为字典，然后将其映射到数组，如下所示

 results = [ { unit: 5, date: '2015-12-04 00:01:00' }, { unit: 10, date: '2015-12-04 00:01:00' }, { unit: 5, date: '2015-12-04 00:31:00' }, { unit: 9, date: '2015-12-04 00:31:00' }, { unit: 5, date: '2015-12-04 01:01:00' }, { unit: 10, date: '2015-12-04 01:01:00' }, { unit: 10, date: '2015-12-04 01:31:00' }, { unit: 5, date: '2015-12-04 01:31:00' }, { unit: 10, date: '2015-12-04 02:01:00' }, { unit: 5, date: '2015-12-04 02:01:00' }, { unit: 5, date: '2015-12-04 02:31:00' }, { unit: 9, date: '2015-12-04 02:31:00' }, { unit: 5, date: '2015-12-04 03:01:00' }, { unit: 9, date: '2015-12-04 03:01:00' }, { unit: 5, date: '2015-12-04 03:31:00' }, { unit: 10, date: '2015-12-04 03:31:00' }, { unit: 10, date: '2015-12-04 04:01:00' }, { unit: 5, date: '2015-12-04 04:01:00' }] // first make an object with {date: unit} value as such const newResults = results.reduce((acc, item) => ({ ...acc, [item.date]: (acc[item.date] || 0) + item.unit }) , {}) console.log(newResults) /* { "2015-12-04 00:01:00": 15, "2015-12-04 00:31:00": 14, "2015-12-04 01:01:00": 15, "2015-12-04 01:31:00": 15, "2015-12-04 02:01:00": 15, "2015-12-04 02:31:00": 14, "2015-12-04 03:01:00": 14, "2015-12-04 03:31:00": 15, "2015-12-04 04:01:00": 15 } */ // now if you want array representation for this you can do const finalResult = Object.keys(newResults).map(key => ({date: key, unit: newResults[key]})) console.log(finalResult) /* [ { "date": "2015-12-04 00:01:00", "unit": 15 }, { "date": "2015-12-04 00:31:00", "unit": 14 }, { "date": "2015-12-04 01:01:00", "unit": 15 }, { "date": "2015-12-04 01:31:00", "unit": 15 }, { "date": "2015-12-04 02:01:00", "unit": 15 }, { "date": "2015-12-04 02:31:00", "unit": 14 }, { "date": "2015-12-04 03:01:00", "unit": 14 }, { "date": "2015-12-04 03:31:00", "unit": 15 }, { "date": "2015-12-04 04:01:00", "unit": 15 } ] */ 

Answer 2

您应该按日期将其分组到一个新元素中，然后使用单位总和创建一个新数组

let indexedDates = {};
results.forEach(result => {
   let arrayByDate = indexedDates[result.date] || [];
   arrayByDate.push(result.unit);
   indexedDates[result.date] = arrayByDate;
});
let yourExpectedResult = Object.keys(indexedDates).map(date => ({
  date,
  unit: indexedDates[date].reduce((a, b) => a +b)
}));

 let results = [ { unit: 5, date: '2015-12-04 00:01:00' }, { unit: 10, date: '2015-12-04 00:01:00' }, { unit: 5, date: '2015-12-04 00:31:00' }, { unit: 9, date: '2015-12-04 00:31:00' }, { unit: 5, date: '2015-12-04 01:01:00' }, { unit: 10, date: '2015-12-04 01:01:00' }, { unit: 10, date: '2015-12-04 01:31:00' }, { unit: 5, date: '2015-12-04 01:31:00' }, { unit: 10, date: '2015-12-04 02:01:00' }, { unit: 5, date: '2015-12-04 02:01:00' }, { unit: 5, date: '2015-12-04 02:31:00' }, { unit: 9, date: '2015-12-04 02:31:00' }, { unit: 5, date: '2015-12-04 03:01:00' }, { unit: 9, date: '2015-12-04 03:01:00' }, { unit: 5, date: '2015-12-04 03:31:00' }, { unit: 10, date: '2015-12-04 03:31:00' }, { unit: 10, date: '2015-12-04 04:01:00' }, { unit: 5, date: '2015-12-04 04:01:00' }]; let indexedDates = {}; results.forEach(result => { let arrayByDate = indexedDates[result.date] || []; arrayByDate.push(result.unit); indexedDates[result.date] = arrayByDate; }); let yourExpectedResult = Object.keys(indexedDates).map(date => ({ date, unit: indexedDates[date].reduce((a, b) => a +b) })); console.log(yourExpectedResult); 

Answer 3

您需要使累加器reduce一个键为日期的对象。 然后，您可以在units属性中累积。

您可以使用Object.values()将其转换回数组。

 results = [ { unit: 5, date: '2015-12-04 00:01:00' }, { unit: 10, date: '2015-12-04 00:01:00' }, { unit: 5, date: '2015-12-04 00:31:00' }, { unit: 9, date: '2015-12-04 00:31:00' }, { unit: 5, date: '2015-12-04 01:01:00' }, { unit: 10, date: '2015-12-04 01:01:00' }, { unit: 10, date: '2015-12-04 01:31:00' }, { unit: 5, date: '2015-12-04 01:31:00' }, { unit: 10, date: '2015-12-04 02:01:00' }, { unit: 5, date: '2015-12-04 02:01:00' }, { unit: 5, date: '2015-12-04 02:31:00' }, { unit: 9, date: '2015-12-04 02:31:00' }, { unit: 5, date: '2015-12-04 03:01:00' }, { unit: 9, date: '2015-12-04 03:01:00' }, { unit: 5, date: '2015-12-04 03:31:00' }, { unit: 10, date: '2015-12-04 03:31:00' }, { unit: 10, date: '2015-12-04 04:01:00' }, { unit: 5, date: '2015-12-04 04:01:00' }]; arr = Object.values(results.reduce((a, { unit, date }) => (a[date] = { date: date, unit: a[date] ? a[date].unit + unit : unit }, a), {})); console.log(arr); 

Answer 4

我想你要这个吗？

const x = results.reduce((accu, r) => {
    const { unit, date } = r;
    accu[date] = accu[date] || { unit: 0, date };
    accu[date].unit += unit;
    return accu;
}, {});
const yourNeed = Object.values(x);