按键按数据分组，并返回包含另一个键和值的新对象。

Question

我有这样的数据：

const data = [
  {name: 'alice', colors: ['red', 'blue'], count: 1, day: '2018-11-12'},
  {name: 'duke', colors: ['red', 'blue'], count: 1, day: '2018-12-12'},
  {name: 'bob', colors: ['blue'], count: 1, day: '2018-11-11'},
  {name: 'alice', colors: ['blue'], count: 1, day: '2018-11-10'},
  {name: 'carl', colors: ['blue'], count: 3, day: '2018-11-01'},
  {name: 'bob', colors: ['red'], count: 1, day: '2017-11-12'},
  {name: 'bob', colors: [], count: 1, day: '2018-11-12'},
  {name: 'bob', colors: ['red', 'blue', 'yellow'], count: 1, day: '2018-11-11'},
  {name: 'alice', colors: ['yellow'], count: 2, day: '2018-11-11'},
  {name: 'duke', colors: ['red', 'yellow'], count: 1, day: '2018-11-12'},
];

现在，我希望按数据按日分组，并获得键计数的总和，从而获得这样的对象数组：

const newData = [
  {day: '2018-11-12', countSum: 5}, // sum of {name: 'alice', colors: ['red', 'blue'], count: 1, day: '2018-11-12'}, {name: 'alice', colors: [blue'], count: 2, day: '2018-11-12'}, {name: 'bob', colors: [], count: 1, day: '2018-11-12'}, {name: 'duke', colors: ['red', 'yellow'], count: 1, day: '2018-11-12'}
  {day: '2018-12-12', countSum: 1},
  {day: '2018-11-11', countSum: 2}, // sum of {name: 'bob', colors: [blue'], count: 1, day: '2018-11-11'}, {name: 'bob', colors: ['red', 'blue', 'yellow'], count: 1, day: '2018-11-11'}
  {day: '2018-11-10', countSum: 1},
  {day: '2018-11-01', countSum: 3},
  {day: '2017-11-12', countSum: 1},
]

我试着在白天使用Lodash的groupBy对数据进行分组，但无法计算计数键的总和。我需要帮助。

非常感谢

Answer 1

与charlietfl的“减少”解决方案类似，您也可以使用for..of。

​

const data = [
  {name: 'alice', colors: ['red', 'blue'], count: 1, day: '2018-11-12'},
  {name: 'duke', colors: ['red', 'blue'], count: 1, day: '2018-12-12'},
  {name: 'bob', colors: ['blue'], count: 1, day: '2018-11-11'},
  {name: 'alice', colors: ['blue'], count: 1, day: '2018-11-10'},
  {name: 'carl', colors: ['blue'], count: 3, day: '2018-11-01'},
  {name: 'bob', colors: ['red'], count: 1, day: '2017-11-12'},
  {name: 'bob', colors: [], count: 1, day: '2018-11-12'},
  {name: 'bob', colors: ['red', 'blue', 'yellow'], count: 1, day: '2018-11-11'},
  {name: 'alice', colors: ['yellow'], count: 2, day: '2018-11-11'},
  {name: 'duke', colors: ['red', 'yellow'], count: 1, day: '2018-11-12'},
];

let result = {}

for(let d of data) {
  result[d.day] = result[d.day] || { day: d.day, countSum: 0}
  result[d.day].countSum += d['count']
}

console.log(Object.values(result))

​

Answer 2

可以使用Array#reduce()创建一个以公共属性值(day)作为键的对象，然后使用Object.values()返回预期的数组。

​

const counts = data.reduce((a, {day, count}) => {
   a[day] = a[day] || {day, countSum:0}
   a[day].countSum += count
   return a
},{})

const res = Object.values(counts)

console.log(res)

<script>
const data = [
  {name: 'alice', colors: ['red', 'blue'], count: 1, day: '2018-11-12'},
  {name: 'alice', colors: ['blue'], count: 2, day: '2018-11-12'},
  {name: 'duke', colors: ['red', 'blue'], count: 1, day: '2018-12-12'},
  {name: 'bob', colors: ['blue'], count: 1, day: '2018-11-11'},
  {name: 'alice', colors: ['blue'], count: 1, day: '2018-11-10'},
  {name: 'carl', colors: ['blue'], count: 3, day: '2018-11-01'},
  {name: 'bob', colors: ['red'], count: 1, day: '2017-11-12'},
  {name: 'bob', colors: [], count: 1, day: '2018-11-12'},
  {name: 'bob', colors: ['red', 'blue', 'yellow'], count: 1, day: '2018-11-11'},
  {name: 'alice', colors: ['yellow'], count: 2, day: '2018-11-11'},
  {name: 'duke', colors: ['red', 'yellow'], count: 1, day: '2018-11-12'},
]
</script>

​

Answer 3

下面是一种房客方法。首先groupBy day，然后映射该组的每个结果，然后由count对每个组执行sumBy，就是这样

​

var data = [{"name":"alice","colors":["red","blue"],"count":1,"day":"2018-11-12"},{"name":"duke","colors":["red","blue"],"count":1,"day":"2018-12-12"},{"name":"bob","colors":["blue"],"count":1,"day":"2018-11-11"},{"name":"alice","colors":["blue"],"count":1,"day":"2018-11-10"},{"name":"carl","colors":["blue"],"count":3,"day":"2018-11-01"},{"name":"bob","colors":["red"],"count":1,"day":"2017-11-12"},{"name":"bob","colors":[],"count":1,"day":"2018-11-12"},{"name":"bob","colors":["red","blue","yellow"],"count":1,"day":"2018-11-11"},{"name":"alice","colors":["yellow"],"count":2,"day":"2018-11-11"},{"name":"duke","colors":["red","yellow"],"count":1,"day":"2018-11-12"}];

var res =_(data)
           .groupBy('day')
           .map((grp, day) => ({day, countSum: _.sumBy(grp, 'count')}))
           .value();

console.log(res);

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

​