在不改变原始数组的情况下在数组中添加对象的算法

Question

我有一系列待处理的付款作为对象，我想知道同一家商店的所有付款的总和。 一旦函数正确计算就调用该函数，当我再次调用该函数时，它将使对象的原始数组发生变化。 我不明白为什么要在其上进行映射时对其进行突变。

我需要该功能不使对象的原始数组发生变异。 它应该进行计算，只是给我结果。 如果再次调用，则也不会将当前总和相加。 它应该从头开始。

let pending = [ 
{Date: "20/12/2018",
Company:[ 
{Name: "Asda", Amount: 5.5},
{Name: "M&S", Amount: 10},
{Name: "Nisa", Amount: 15},
{Name: "Iceland", Amount: 10},
{Name: "Tesco", Amount: 5}
]},
{Date: "20/12/2018",
Company:[ 
{Name: "Asda", Amount: 5.5},
{Name: "M&S", Amount: 10},
{Name: "Nisa", Amount: 15},
{Name: "Iceland", Amount: 10},
{Name: "Tesco", Amount: 5}
]},
{Date: "20/12/2018",
Company:[ 
{Name: "Asda", Amount: 5.5},
{Name: "M&S", Amount: 10},
{Name: "Nisa", Amount: 15},
{Name: "Iceland", Amount: 10},
{Name: "Tesco", Amount: 5}
]},
{Date: "20/12/2018",
Company:[ 
{Name: "Asda", Amount: 5.5},
{Name: "M&S", Amount: 10},
{Name: "Nisa", Amount: 15},
{Name: "Iceland", Amount: 10},
{Name: "Tesco", Amount: 5}
]}
]

function returnSpendTotals() {
  let sumSpend = []
  let spendArray = pending.map(activities => activities.Company)
  spendArray.flat().forEach(spend => {
    let shopName = sumSpend.find(item => item.Name === spend.Name)
    if (shopName) {
      shopName.Amount += spend.Amount
    } else {
      sumSpend.push(spend)
    }
  })
  return sumSpend
}

它应该在每次我调用returnSpendTotals（）时返回

[{Name: "Asda", Amount: 22},
{Name: "M&S", Amount: 40},
{Name: "Nisa", Amount: 60},
{Name: "Iceland", Amount: 40},
{Name: "Tesco", Amount: 20}]

但是如果我第二次打电话给我，这就是我得到的

[{Name: "Asda", Amount: 38.5},
{Name: "M&S", Amount: 70},
{Name: "Nisa", Amount: 105},
{Name: "Iceland", Amount: 70},
{Name: "Tesco", Amount: 35}]

现在有待处理的第一个对象

{Company: [
{Name: "Asda", Amount: 38.5},
{Name: "M&S", Amount: 70},
{Name: "Nisa", Amount: 105},
{Name: "Iceland", Amount: 70},
{Name: "Tesco", Amount: 35}],
Date: "20/12/2018"}

其余待处理的对象保持不变

Answer 1

当您找到一家商店时：

let shopName = sumSpend.find(item => item.Name === spend.Name)

您可以获得对数据结构中的对象的引用 。 然后，您的代码修改该对象：

      shopName.Amount += spend.Amount

我不确定确切的建议是解决方案，因为尚不清楚您要做什么。 可能您应该保持单独的运行总计，而不是更改“ shop”对象。

还要注意， .map()进程在您的函数的早期：

let spendArray = pending.map(activities => activities.Company)

同样会产生一个列表，该列表由返回原始数据结构的引用组成。

Answer 2

使用此解决方案，它很简单，有效，没有任何幻想，只需创建一个对象，为该对象分配属性，然后遍历数据对象即可。

 const data=[{Date:"20/12/2018",Company:[{Name:"Asda",Amount:5.5},{Name:"M&S",Amount:10},{Name:"Nisa",Amount:15},{Name:"Iceland",Amount:10},{Name:"Tesco",Amount:5}]},{Date:"20/12/2018",Company:[{Name:"Asda",Amount:5.5},{Name:"M&S",Amount:10},{Name:"Nisa",Amount:15},{Name:"Iceland",Amount:10},{Name:"Tesco",Amount:5}]},{Date:"20/12/2018",Company:[{Name:"Asda",Amount:5.5},{Name:"M&S",Amount:10},{Name:"Nisa",Amount:15},{Name:"Iceland",Amount:10},{Name:"Tesco",Amount:5}]},{Date:"20/12/2018",Company:[{Name:"Asda",Amount:5.5},{Name:"M&S",Amount:10},{Name:"Nisa",Amount:15},{Name:"Iceland",Amount:10},{Name:"Tesco",Amount:5}]}]; const companies = {}; data.forEach(obj => obj.Company.forEach(o => { companies[o.Name] = companies[o.Name] == null ? 0 : companies[o.Name]; companies[o.Name] += o.Amount; })); console.log(companies); 

编辑

这很相似，只是花哨了一点……这是受到Nina Scholz的回答的启发，我是语法的爱好者。

 const pending = [{ Date: "20/12/2018", Company: [{ Name: "Asda", Amount: 5.5 }, { Name: "M&S", Amount: 10 }, { Name: "Nisa", Amount: 15 }, { Name: "Iceland", Amount: 10 }, { Name: "Tesco", Amount: 5 }] }, { Date: "20/12/2018", Company: [{ Name: "Asda", Amount: 5.5 }, { Name: "M&S", Amount: 10 }, { Name: "Nisa", Amount: 15 }, { Name: "Iceland", Amount: 10 }, { Name: "Tesco", Amount: 5 }] }, { Date: "20/12/2018", Company: [{ Name: "Asda", Amount: 5.5 }, { Name: "M&S", Amount: 10 }, { Name: "Nisa", Amount: 15 }, { Name: "Iceland", Amount: 10 }, { Name: "Tesco", Amount: 5 }] }, { Date: "20/12/2018", Company: [{ Name: "Asda", Amount: 5.5 }, { Name: "M&S", Amount: 10 }, { Name: "Nisa", Amount: 15 }, { Name: "Iceland", Amount: 10 }, { Name: "Tesco", Amount: 5 }] }]; const compelte = pending.reduce((r, { Company }) => { Company.forEach(({ Name, Amount }) => r[Name] == null ? r[Name] = 0 : r[Name] += Amount); return r; }, {}); console.log(compelte); 

Answer 3

您可以采用已分解的属性，并为结果集构建一个新对象，以防止相同的对象引用所使用的数据。

 function returnSpendTotals() { return pending.reduce((r, { Company }) => { Company.forEach(({ Name, Amount }) => { let shop = r.find(item => item.Name === Name) if (shop) { shop.Amount += Amount; } else { r.push({ Name, Amount }); } }); return r; }, []); } let pending = [{ Date: "20/12/2018", Company: [{ Name: "Asda", Amount: 5.5 }, { Name: "M&S", Amount: 10 }, { Name: "Nisa", Amount: 15 }, { Name: "Iceland", Amount: 10 }, { Name: "Tesco", Amount: 5 }] }, { Date: "20/12/2018", Company: [{ Name: "Asda", Amount: 5.5 }, { Name: "M&S", Amount: 10 }, { Name: "Nisa", Amount: 15 }, { Name: "Iceland", Amount: 10 }, { Name: "Tesco", Amount: 5 }] }, { Date: "20/12/2018", Company: [{ Name: "Asda", Amount: 5.5 }, { Name: "M&S", Amount: 10 }, { Name: "Nisa", Amount: 15 }, { Name: "Iceland", Amount: 10 }, { Name: "Tesco", Amount: 5 }] }, { Date: "20/12/2018", Company: [{ Name: "Asda", Amount: 5.5 }, { Name: "M&S", Amount: 10 }, { Name: "Nisa", Amount: 15 }, { Name: "Iceland", Amount: 10 }, { Name: "Tesco", Amount: 5 }] }]; console.log(returnSpendTotals()); 

Answer 4

function returnSpendTotals() {
  let companies = {}
  pending.forEach(item => {
      item.Company.forEach(company => {
          if (!companies[company.Name]) {
              companies[company.Name] = company.Amount;
          } else {
              companies[company.Name] += company.Amount;
          }
      })
  })
  return companies
}

returnSpendTotals(pending)

// result:  {Asda: 22, M&S: 40, Nisa: 60, Iceland: 40, Tesco: 20}