Question

我有一个对象数组：

var myArray = [
    {
        "date" : "03/01/2017",
        "value" : 2
    },  {
        "date" : "04/01/2017",
        "value" : 6
    },  {
        "date" : "05/01/2017",
        "value" : 4
    }
];

我需要累计值并使用更新的值保持相同的数组

结果看起来像这样

var myArray = [
    {
        "date" : "03/01/2017",
        "value" : 2
    },  {
        "date" : "04/01/2017",
        "value" : 8 //(2+6)
    },  {
        "date" : "05/01/2017",
        "value" : 12 //(2+6+4)
    }
];

我知道这存在

[0, 1, 2, 3, 4].reduce(function(accumulator, currentValue, currentIndex, array) {
  return accumulator + currentValue;
});

但是我找不到一个对象返回对象的例子

Answer 1

使用Array.prototype.forEach的此参数累积值 - 请参阅下面的演示：

＆＃13;

var myArray=[{"date":"03/01/2017","value":2},{"date":"04/01/2017","value":6},{"date":"05/01/2017","value":4}];

myArray.forEach(function(e){
  this.count = (this.count || 0) +  e.value;
  e.value = this.count;
},Object.create(null));

console.log(myArray);

＆＃13;

.as-console-wrapper{top:0;max-height:100%!important;}

＆＃13;

Answer 2

您可以使用map()和Object.assign()复制对象。

＆＃13;

var myArray = [{
  "date": "03/01/2017",
  "value": 2
}, {
  "date": "04/01/2017",
  "value": 6
}, {
  "date": "05/01/2017",
  "value": 4
}];

var result = myArray.map(function(o) {
  var obj = Object.assign({}, o)
  obj.value = this.total += o.value
  return obj
}, {total: 0})

console.log(result)

＆＃13;

Answer 3

作为一个不同的示例并在var myArray = [ { "date" : "03/01/2017", "value" : 2 }, { "date" : "04/01/2017", "value" : 6 }, { "date" : "05/01/2017", "value" : 4 } ]; function accumulate() { var count = 0; return myArray.reduce(function(acc, cur) { count += cur.value || 0; cur.value = count; acc.push(cur); return acc; }, []); } console.log(accumulate(myArray));上回答您的问题，您将以这种方式使用reduce

{{1}}

Answer 4

简单forEach，可以在适当的位置改变数组。

var myArray = [
    {
        "date" : "03/01/2017",
        "value" : 2
    },  
    {
        "date" : "04/01/2017",
        "value" : 6
    },  
    {
        "date" : "05/01/2017",
        "value" : 4
    }
];

myArray.forEach(
  (e,i,arr) => e.value += i && arr[i-1].value // only fires if i is truthy (i>0)
);      

console.log(myArray);

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Javascript累积一个对象数组到一个对象数组

4 个答案: