javascript - 如何使用 Lodash 按多个键分组并将其值汇总到对象数组中？

Question

在下面的数组中，我想按 item 分组和 reason ，然后计算总数quantity :

item_movements = [
  {
    item: "Apple",
    reason: 1,
    quantity: 5
  },
  {
    item: "Banana",
    reason: 2,
    quantity: 10
  },
  {
    item: "Apple",
    reason: 1,
    quantity: 5
  },
  {
    item: "Banana",
    reason: 1,
    quantity: 8
  },
  {
    item: "Apple",
    reason: 2,
    quantity: 3
  },
  {
    item: "Banana",
    reason: 1,
    quantity: 8
  }
];

我想要达到的结果是这样的:

item_totals = [
  {
    item: "Apple",
    1: 10,
    2: 3
  },
  {
    item: "Banana",
    1: 16,
    2: 10
  }
];

我可以按 item 分组像这样使用 Loadash:

({
  itemMovementbyItem() {
    var result = _(this.item_movements)
      .groupBy(x => x.item)
      .map((value, key) => ({
        item: key,
        item_movements: value
      }))
      .value()

    return result
  }
})

但是我在按 reason 进行第二次分组时遇到问题.

Answer 1

您可以在按 'item' 分组后直接对属性求和.

function itemMovementbyItem(array) {
    return _(array)
        .groupBy('item')
        .map(group => ({
            item: group[0].item,
            1: _.sumBy(group, o => o.reason === 1 ? o.quantity : 0),
            2: _.sumBy(group, o => o.reason === 2 ? o.quantity : 0)
        }))
        .value();
}

var item_movements = [{ item: "Apple", reason: 1, quantity: 5 }, { item: "Banana", reason: 2, quantity: 10 }, { item: "Apple", reason: 1, quantity: 5 }, { item: "Banana", reason: 1, quantity: 8 }, { item: "Apple", reason: 2, quantity: 3 }, { item: "Banana", reason: 1, quantity: 8 }];

console.log(itemMovementbyItem(item_movements));

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