如何通过一些键求和数组中的对象值？

Question

我找不到解决此问题的方法。

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，我想要这样的结果：

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。 我将松开对象的原始结构。

解决我的问题的正确方法是什么？

Answer 1

将每个组的第一个对象散布到结果对象中，以获得重复出现的属性：

 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); 

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

Answer 2

这将起作用。 简单的减少。 您不需要为此使用lodash 。

const results = taxItems.reduce(function(sum, taxItem) {

    let index = sum.map(item => item.taxCode).indexOf(taxItem.taxCode);
    if (index == -1) {
        sum.push(taxItem);
    } else {
        sum[index].taxAmount = sum[index].taxAmount + taxItem.taxAmount;
    }

    return sum;
}, []);

//results 
//[{"taxCode":"430","taxAmount":12,"ItemTaxPercentage":20,"taxCategory":"2"}{"taxCode":"431","taxAmount":5,"ItemTaxPercentage":20,"taxCategory":"2"}]

Answer 3

使用简单的reduce可以做到这一点。

 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' } ] let op = Object.values(taxItems.reduce((op,cur)=>{ if(op[cur['taxCode']]){ op[cur['taxCode']]['taxAmount']+= cur['taxAmount']; } else { op[cur['taxCode']] = cur } return op; },{})) console.log(op) 

Answer 4

您也可以通过_.map ， _.groupBy和_.mergeWith解决此_.mergeWith ：

 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 result = _.map(_.groupBy(taxItems, 'taxCode'), x => _.mergeWith(...x, (o,s,k) => k == 'taxAmount' ? o+s : s)) console.log(result) 

 <script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.10/lodash.min.js"></script>