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JS reduce列表基于它的一个属性

reduce list reactjs arrays javascript

sefirosu · 技术社区 · 7 年前

我正在用react js编写一个方法,假设我有如下列表。

const itemList = [
    {
        "id": 3295042,
        "tillPoint": "A",
        "date": "23/01/2019",
        "AnnaIncome": 100,
        "PeterIncome": 50,
        "KenIncome": 100,
        "freeCash": 30
    },
    {
        "id": 3295042,
        "tillPoint": "B",
        "date": "23/01/2019",
        "AnnaIncome": 300,
        "PeterIncome": 200,
        "KenIncome": 100,
        "freeCash": 50
    },
    {
        "id": 3295042,
        "tillPoint": "A",
        "date": "22/01/2019",
        "AnnaIncome": 120,
        "PeterIncome": 120,
        "KenIncome": 30,
        "freeCash": 50
    },
    {
        "id": 3295042,
        "tillPoint": "B",
        "date": "22/01/2019",
        "AnnaIncome": 100,
        "PeterIncome": 150,
        "KenIncome": 50,
        "freeCash": 60
    },
]

.reduce 为了使列表仅按日期属性包含较少的项。例如,在上面的列表中,实际上只有两个日期:2019年1月22日和2019年1月23日。我希望按每个对象的日期缩小列表的大小。因此,每个人的收入将以自己的名义加起来。最终,列表将变成只有2个对象。并且在新列表中删除了某些属性 e、 g下面的“id”和“tillpoint”被删除,其余属性加在一起:

let itemList = [
    {
        "date": "23/01/2019",
        "AnnaIncome": 300,
        "PeterIncome": 250,
        "KenIncome": 200,
        "freeCash": 80
    },
    {
        "date": "22/01/2019",
        "AnnaIncome": 220,
        "PeterIncome": 280,
        "KenIncome": 80,
        "freeCash": 110
    }
]

我在这里尝试的是下面的内容,但它不起作用。

itemList.reduce((a, b) => ({ date: a.AnnaIncome + b.AnnaIncome, a.PeterIncome + b.PeterIncome, a.KenIncome + b.KenIncome, a.freeCash + b.freeCash }));

3 回复 | 直到 7 年前

Jonas Wilms 7 年前

您必须按日期分组,这可以使用哈希表轻松完成:

 const byDate = new Map;

 for(const { date, id, tillPoint, ...rest } of itemList) {
   if(byDate.has(date)) {
     const dupe = byDate.get(date);
     for(const [k, v] of Object.entries(rest))
       dupe[k] += v;
   } else {
     byDate.set(date, { date, ...rest });
   }
}

const result = [...byDate.values()];

当然,您可以轻松地将添加内容硬编码为 dupe.something += rest.something

Code Maniac 7 年前

你可以用 reduce spread 操作人员

所以这里我要做的是,我获取你想要直接添加到输出中的动态属性,而不需要任何操作 ...rest

然后我检查数据键是否已经存在,然后添加加 freeCash 现有价值。如果没有,我们将创建一个带有日期和相应值的新键。

const itemList = [{"id":3295042,"tillPoint":"A","date":"23/01/2019","AnnaIncome":100,"PeterIncome":50,"KenIncom":100,"freeCash":30},{"id":3295042,"tillPoint":"B","date":"23/01/2019","AnnaIncome":300,"PeterIncome":200,"KenIncom":100,"freeCash":50},{"id":3295042,"tillPoint":"A","date":"22/01/2019","AnnaIncome":120,"PeterIncome":120,"KenIncom":30,"freeCash":50},{"id":3295042,"tillPoint":"B","date":"22/01/2019","AnnaIncome":100,"PeterIncome":150,"KenIncom":50,"freeCash":60},]

const op = itemList.reduce((output,current)=>{
  let {id,tillPoint,date,freeCash,...rest} = current
 
  if(output[date]){
    output[date] = {
      ...output[date],
      ...rest,
      date,
      freeCash: output[date].freeCash +freeCash
    }
  } else {
    output[date] ={
      ...rest,
      date,
      freeCash
    }
  }
  return output
},{})

console.log(Object.values(op))

mscdeveloper 7 年前

const itemList = [
    { "id": 3295042, "tillPoint": "A", "date": "23/01/2019", "AnnaIncome": 100, "PeterIncome": 50,  "KenIncome": 100, "freeCash": 30 },
    { "id": 3295042, "tillPoint": "B", "date": "23/01/2019", "AnnaIncome": 300, "PeterIncome": 200, "KenIncome": 100, "freeCash": 50 },
    { "id": 3295042, "tillPoint": "A", "date": "22/01/2019", "AnnaIncome": 120, "PeterIncome": 120, "KenIncome": 30,  "freeCash": 50 },
    { "id": 3295042, "tillPoint": "B", "date": "22/01/2019", "AnnaIncome": 100, "PeterIncome": 150, "KenIncome": 50,  "freeCash": 60 },
];


var new_itemList=[];

for(var key in itemList){
	var new_key = -1;
	for(var keyn in new_itemList){
	   if(new_itemList[keyn].date == itemList[key].date){
	   	  new_key = parseInt(keyn, 10);
	   }
	}
	if(new_key == -1){
		new_itemList.push({'date':itemList[key].date, 'AnnaIncome': itemList[key].AnnaIncome, 'PeterIncome': itemList[key].PeterIncome, 'KenIncome': itemList[key].KenIncome, 'freeCash': itemList[key].freeCash});
	}else{
       new_itemList[new_key].AnnaIncome +=  itemList[key].AnnaIncome;
       new_itemList[new_key].PeterIncome +=  itemList[key].PeterIncome;
       new_itemList[new_key].KenIncome +=  itemList[key].KenIncome;
       new_itemList[new_key].freeCash +=  itemList[key].freeCash;
	}
}
console.log(new_itemList);