Question

我正在尝试将新生成的对象推入JavaScript中的数组

我有一个以下形式的数组：

savings: any = [{month: "January", amount: 300}, {month: "February",  amount:450}, {month: "March", amount: 500}]

和一个名为 savings_bf 的变量，其值是

savings_bf = 15000

我使用了数组 Savings 和 Savings_bf 中的 amount 值，使用此处提供的解决方案{{3} }以获取输出：

_total_cf = [15300,15750,16250]

我的代码如下；

savings.forEach(s =>s.total_cf = _total_cf)

新的储蓄数组的预期输出应为：

[{month: "January", amount: 300, total_cf: 15300 }, {month: "February",  amount:450, total_cf: 15750}, {month: "March", amount: 500 total_cf: 16250}]

实际输出：

[{month: "January", amount: 300, total_cf: [15300,15750,16250]}, {month: "February",  amount:450, total_cf: [15300,15750,16250]}, {month: "March", amount: 500 total_cf: [15300,15750,16250]}]

Answer 1

//  You can use following code.
savings.forEach((item, index, array) => {
    savings[index].total_cf = _total_cf[index];
});

Answer 2

您可以使用forEach提供的回调方法的第二个参数来跟踪索引。由于_total_cf是一个数组，因此您需要根据索引访问适当的项目。您可以在回调中使用索引，如下所示：

var savings = [{month: "January", amount: 300}, {month: "February",  amount:450}, {month: "March", amount: 500}]

var _total_cf = [15300,15750,16250];

savings.forEach((s, index) => s.total_cf = _total_cf[index]) ;

console.log(savings);

Answer 3

仅.map()个数组，添加您在循环中更新的运行总计。

const months = [
  {month: "January", amount: 300},
  {month: "February",  amount:450},
  {month: "March", amount: 500}
];
const savings = 15000;
let running_total = savings;
const updated_months = months.map( item => {
  running_total += item.amount;
  return {
    month: item.month,
    amount: running_total
  };
});
console.log( updated_months );

如果由于某种原因您还需要_total_cf变量来进行其他操作，则可以轻松地再次提取它：

const updated_months = [
  {month: "January", amount: 15300},
  {month: "February",  amount:15750},
  {month: "March", amount: 16250}
];

const _total_cf = updated_months.map( item => item.amount );

console.log( _total_cf );

Answer 4

您可以使用Array.prototype.map映射数组中的每个对象，并使用其在回调（第二个参数）中提供的 index 来从{{1} }数组。

还可以使用传播运算符_total_cf与先前的对象属性和...数组中的新对象属性进行合并：

_total_cf

在代码中，您将整个const savings = [{month: "January", amount: 300}, {month: "February", amount:450}, {month: "March", amount: 500}]; const _total_cf = [15300,15750,16250]; const result = savings.map((obj, idx) => ({...obj, total_cf: _total_cf[idx]})); console.log(result);数组分配给您在每次迭代中创建的total_cf属性。

total_cf

还要对//the entire array is assigned to the `total_cf` property. savings.forEach(s =>s.total_cf = _total_cf);的{{1}}数组中的原始对象进行突变。在savings操作中，将返回一个包含新对象的新数组，其中包含旧的道具以及要添加的新属性。

Answer 5

您可以使用正确的方法来计算Savings_bf，并且可以一次完成所有操作。

Answer 6

您还可以使用reduce来计算total_cf

尝试以下代码

const savings = [
  {month: "January", amount: 300},
  {month: "February",  amount:450},
  {month: "March", amount: 500}
];
const savings_bf = 15000;

savings.reduce((a,b)=>{
    b.total_cf = (a[a.length-1] ? a[a.length-1].total_cf : savings_bf) + b.amount 
    a.push(b)
    return a
},[])

如何将具有多个元素的新对象正确地推入数组中？

6 个答案: