javascript - 如何通过某个键对数组中的对象值求和？

Question

我找不到这个问题的解决方案。

我有数组:

const taxItems = [{
    taxCode: '430',
    taxAmount: 2,
    ItemTaxPercentage: 20,
    taxCategory: '2'
  },
  {
    taxCode: '430',
    taxAmount: 4,
    ItemTaxPercentage: 20,
    taxCategory: '2'
  },
  {
    taxCode: '431',
    taxAmount: 5,
    ItemTaxPercentage: 20,
    taxCategory: '2'
  },
  {
    taxCode: '430',
    taxAmount: 6,
    ItemTaxPercentage: 20,
    taxCategory: '2'
  }
]

从这个数组中，我想按taxCode 汇总所有对象。我希望得到如下结果:

var results = [{
    taxCode: '430',
    taxAmount: 12,
    ItemTaxPercentage: 20,
    taxCategory: '2'
  },
  {
    taxCode: '431',
    taxAmount: 5,
    ItemTaxPercentage: 20,
    taxCategory: '2'
  }
]

我尝试使用lodash:

var results =
lodash(taxItems)
  .groupBy('taxCode')
  .map((objs, key) => ({
      'taxCode': key,
      'taxAmount': lodash.sumBy(objs, 'taxAmount') }))
  .value();

但它仅适用于键值对。我将失去对象的原始结构。

解决我的问题的正确方法是什么？

Answer 1

将每组的第一个对象扩展到结果对象中，以获得重复属性:

const taxItems = [{"taxCode":"430","taxAmount":2,"ItemTaxPercentage":20,"taxCategory":"2"},{"taxCode":"430","taxAmount":4,"ItemTaxPercentage":20,"taxCategory":"2"},{"taxCode":"431","taxAmount":5,"ItemTaxPercentage":20,"taxCategory":"2"},{"taxCode":"430","taxAmount":6,"ItemTaxPercentage":20,"taxCategory":"2"}];

const results = _(taxItems)
  .groupBy('taxCode')
  .map((objs, taxCode) => ({
      ..._.head(objs),
      taxCode,
      taxAmount: _.sumBy(objs, 'taxAmount') }))
  .value();
  
console.log(results);

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