javascript - 如何基于对象数组中的相似值（不是属性）对对象数组执行加/减运算

Question

我有一个这样的对象数组：

i/p:

let payments=[ 
  {from:"b",to:"c",amount:30}, {from:"a",to:"c",amount:30},
  {from:"c",to:"a",amount:50}, {from:"b",to:"a",amount:50},
  {from:"c",to:"b",amount:66.66}, {from:"a",to:"b",amount:66.66},
  {from:"a",to:"c",amount:150}, {from:"b",to:"c",amount:150}, 
  {from:"a", to:"c",amount:75}, {from:"b", to:"c",amount:125} 
]

现在我想基于相同的属性值对金额属性执行求和运算，并基于反向匹配属性值（即从，到）对金额属性进行减法运算，将数组减少为：

o/p：

[
  { from: "b", to: "c", amount: 238.34 }, //(sum of all b->c amounts) minus (sum of all c->b amounts)
  { from: "a", to: "c", amount: 205 },    //(sum of all a->c amounts) minus (sum of all c-a amounts)
  { from: "a", to: "b", amount: 16.66 },  //(sum of all a->b amounts) minus (sum of all b->a amounts)
];

注意：结果数组数量属性不应为负

我尝试了一些方法，但无法实现这一点。任何帮助，将不胜感激。谢谢

标签： javascriptobjectjavascript-objectsdynamic-arrays

Answer 1

也许这会有所帮助：

let payments=[ 
  {from:"b",to:"c",amount:30}, {from:"a",to:"c",amount:30},
  {from:"c",to:"a",amount:50}, {from:"b",to:"a",amount:50},
  {from:"c",to:"b",amount:66.66}, {from:"a",to:"b",amount:66.66},
  {from:"a",to:"c",amount:150}, {from:"b",to:"c",amount:150}, 
  {from:"a", to:"c",amount:75}, {from:"b", to:"c",amount:125} 
];

let pay = Object.entries(
  payments.reduce((tot,{from,to,amount})=>{
   let u=from+'-'+to;       // from-to-relationship (in alphabetical order)
   if (to<from) { u=to+'-'+from; amount=-amount }
   tot[u]=(tot[u]||0)+amount;  // collate all payments here
   return tot;
  }, {})
 ).map(([u,a])=>{let ft=u.split('-');
   if (a<0) {ft=ft.reverse();a=-a}
   return {from:ft[0], to:ft[1], amount:a.toFixed(2)}
 })
   
console.log(pay)

在.reduce函数中，我将两个合作伙伴之间的所有付款整理到一个以“from-to”命名的“acounts”的帐户对象中，该名称始终按字母顺序建立，因此，如果我遇到付款，{from:"b", to:"a", amount:123}我会交换订单并使金额为负数：

if (to<from) { u=to+'-'+from; amount=-amount }

完成此操作后，我使用 遍历帐户对象Object.entries。这将允许我再次将帐户名称from与to合作伙伴分开。这次我检查，合伙人之间的应付金额是否为负数。如果是这样，我交换合作伙伴的顺序 ( ft) 并将 amonut ( a) 乘以 -1：

if (a<0) {ft=ft.reverse();a=-a}