Javascript object not appending new attribute

Question

I have this function, where I retrieve an array of objects, I then have a for loop to loop through the objects, and append an index or ind attribute to it:

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)
}

but when I run this, the data is returned as

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

instead of:

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

Please how do I fix this

theres nothing wrong with the code provided can you give us more information on Customers.find() — Joe Warner, Jan 28 '19 at 15:25
try this: `await Customers.find({}, { "_id": 1 }).toArray();` — HMR, Jan 28 '19 at 15:25
Can you please provide the value of `await Customers.find({}, { "_id": 1 })`? So that it will easier to provide a solution. — Deepak Biswal, Jan 28 '19 at 15:26
`Customers.update( { _id: 1 }, { ind: '...' }, { multi: true }, function (err, num) { });` — Yassine Addi, Jan 28 '19 at 15:26
Possible duplicate of [How do I return the response from an asynchronous call?](https://stackoverflow.com/questions/14220321/how-do-i-return-the-response-from-an-asynchronous-call) — connexo, Jan 28 '19 at 15:29
`Customers.find()` [returns a cursor](https://docs.mongodb.com/manual/reference/method/db.collection.find/#db.collection.find), you will [find here](https://docs.mongodb.com/manual/tutorial/iterate-a-cursor/#read-operations-cursors) how to properly use it — Cinn, Jan 28 '19 at 15:30
Then use [`.lean()`](https://mongoosejs.com/docs/api.html#query_Query-lean) — Ashh, Jan 30 '19 at 08:18

score 2 · Answer 1 · answered Jan 28 '19 at 15:26

change your for and turn it into a 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;
}

or instead returning the customer, you can create a completly new customer.

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

score 0 · Answer 2 · answered Jan 28 '19 at 15:25

0

It looks like your objects are freezed, idk what library you are using to fetch those items from your data source, but you can read about object freezing here https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/freeze

answered Jan 28 '19 at 15:25

cojack

2,444
1
17
18

Question is tagged [tag:mongodb] – Hatchet Jan 28 '19 at 15:26

score 0 · Answer 3 · answered Jan 28 '19 at 15:32

Try copying the values over to the individual target objects with Object.assign.

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);
}

score 0 · Answer 4 · answered Jan 30 '19 at 08:19

0

I finally solved it. I think mongoose was messing with it. But adding ._doc seems to have fixed it

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

    let customer = customers[i], 

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

answered Jan 30 '19 at 08:19

Kingsley CA

10,685
10
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Javascript object not appending new attribute

4 Answers4