javascript - 按键对数据进行分组，并返回一个包含另一个键的总和值的新对象

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'},
];

现在我想按天对数据进行分组并获取键计数的总和，以便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},
]

我尝试使用Lodash的groupBy按天对数据进行分组，但我无法计算count key的总和。 我需要帮助。

非常感谢

Answer 1

您可以使用Array#reduce()创建一个以公共(public)属性值(day)为键的对象，然后使用Object.values()返回期望的数组

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>