Question

我有这个函数，我在其中检索对象数组，然后有一个for循环遍历对象，并向其附加索引或ind属性：

module.exports.getCustomers = async (req, res) => {
  let customers = await Customers.find({}, { "_id": 1 });

  for (var i = 0; i < customers.length; i++) {
    customers[i].ind = i;
  }

  console.log(customers)
}

但是当我运行它时，数据返回为

[
  { _id: ... },
  { _id: ... },
  ...
]

代替：

[
   {_id: ..., ind: 0},
   {_id: ..., ind: 1},
   ...
]

请如何解决此问题

Answer 1

更改您的for并将其变成map

module.exports.getCustomers = async (req, res) => {
  let customers = await Customers.find({}, { "_id": 1 });

  let mappedCustomers = customers.map((customer, index) => {
              customer['ind'] = index;
              return customer;
          });


  console.log(mappedCustomers);
  return mappedCustomers;
}

或者代替返回客户，您可以创建一个全新的客户。

let mappedCustomers = customers.map((customer, index) => {
              return {...customer, ind: index};
              });

Answer 2

看来您的对象已冻结，这是您正在使用的库从数据源中提取这些项目的方法，但是您可以在此处https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/freeze

了解有关对象冻结的信息。

Answer 3

尝试使用Object.assign将值复制到各个目标对象。

module.exports.getCustomers = async(req, res) => {
  let customers = await Customers.find({}, {
    "_id": 1
  });

  for (var i = 0; i < customers.length; i++) {
    Object.assign(customers[i], {
      ind: i
    });
  }

  console.log(customers);
}

Answer 4

我终于解决了。我认为mongoose搞砸了。但是添加._doc似乎已经解决了

for (let i = 0; i < customers.length; i++) {

    let customer = customers[i], 

    customer._doc = {
      ...customer._doc,
      index: i
    };
}

Answer 5

您只需替换

customers[i].ind = i;

收件人

customers[i]['ind'] = i;

或者您可以使用前面提到的Object.assign

JavaScript对象未附加新属性

5 个答案: