.exec callback using returns is returning undefined, but console.log do have item in it

Question

I have a mongoose query that will populate from other collection, then will match the populated's query, and then execute a callback function that will filter out null elements. The idea of the code is from https://stackoverflow.com/a/11418489/12773925. However, my return docs is not returning element to orders. Below is my code.

const orders = Order.find()
  .populate('buyer_id', null, { name: { $regex: localQuery } })
  .exec(function (err, docs) {
    docs = docs.filter(function (doc) {
      return doc.buyer_id != null;
    });

    return docs;
  });

When I do console.log(docs), it do have items in it.

The code used for console.log as belows:

const orders = Order.find()
  .populate('buyer_id', null, { name: { $regex: localQuery } })
  .exec(function (err, docs) {
    docs = docs.filter(function (doc) {
      return doc.buyer_id != null;
    });
    console.log(docs);
    return docs;
  });

The returned element as below:

[
  {
    status: 'Completed',
    orderdetails_id: [
      6017f4a79c62e77224b85644,
      6016d2edcc40583748e42908,
      601a4ea674e6ce505ccbd305
    ],
    _id: 6017587bbb33107e8c8f135a,
    buyer_id: {
      role: 'user',
      _id: 6013e314958b9a3570d04a04,
      name: 'Wan Amin',
      createdAt: 2021-01-29T10:27:32.123Z,
      updatedAt: 2021-02-09T07:29:18.396Z,
      __v: 78
    },
    address: [ [Object] ],
    total_price: 446,
    createdAt: 2021-02-01T01:25:15.999Z,
    updatedAt: 2021-02-19T15:44:55.605Z,
    __v: 9,
    driver_id: 60143a2e958b9a3570d04ae6
  }

However, when I check my orders, it is showing undefined.

Answer 1

you can use async/await

const orders = async ()=>{
  let docs = await Order.find().populate('buyer_id', null, { name: { $regex: localQuery } })
  docs = docs.filter(function (doc) { return doc.buyer_id != null; });
  return docs 
  }