Push items into mongo array via mongoose

Question

I\'ve scoured SO a good bit looking for the answer but I\'m sure that I\'m lost for the right words to describe what I\'m after.

Basically I have a mongodb collection

Answer 1

The $push operator appends a specified value to an array.

{ $push: { <field1>: <value1>, ... } }

$push adds the array field with the value as its element.

Above answer fulfils all the requirements, but I got it working by doing the following

var objFriends = { fname:"fname",lname:"lname",surname:"surname" };
Friend.findOneAndUpdate(
   { _id: req.body.id }, 
   { $push: { friends: objFriends  } },
  function (error, success) {
        if (error) {
            console.log(error);
        } else {
            console.log(success);
        }
    });
)

Answer 2

In my case, I did this

  const eventId = event.id;
  User.findByIdAndUpdate(id, { $push: { createdEvents: eventId } }).exec();

Answer 3

I ran into this issue as well. My fix was to create a child schema. See below for an example for your models.

---- Person model

const mongoose = require('mongoose');
const SingleFriend = require('./SingleFriend');
const Schema   = mongoose.Schema;

const productSchema = new Schema({
  friends    : [SingleFriend.schema]
});

module.exports = mongoose.model('Person', personSchema);

***Important: SingleFriend.schema -> make sure to use lowercase for schema

--- Child schema

const mongoose = require('mongoose');
const Schema   = mongoose.Schema;

const SingleFriendSchema = new Schema({
  Name: String
});

module.exports = mongoose.model('SingleFriend', SingleFriendSchema);

Answer 4

Assuming, var friend = { firstName: 'Harry', lastName: 'Potter' };

There are two options you have:

Update the model in-memory, and save (plain javascript array.push):

person.friends.push(friend);
person.save(done);

or

PersonModel.update(
    { _id: person._id }, 
    { $push: { friends: friend } },
    done
);

I always try and go for the first option when possible, because it'll respect more of the benefits that mongoose gives you (hooks, validation, etc.).

However, if you are doing lots of concurrent writes, you will hit race conditions where you'll end up with nasty version errors to stop you from replacing the entire model each time and losing the previous friend you added. So only go to the former when it's absolutely necessary.

Answer 5

An easy way to do that is to use the following:

var John = people.findOne({name: "John"});
John.friends.push({firstName: "Harry", lastName: "Potter"});
John.save();

Answer 6

First I tried this code

const peopleSchema = new mongoose.Schema({
  name: String,
  friends: [
    {
      firstName: String,
      lastName: String,
    },
  ],
});
const People = mongoose.model("person", peopleSchema);
const first = new Note({
  name: "Yash Salvi",
  notes: [
    {
      firstName: "Johnny",
      lastName: "Johnson",
    },
  ],
});
first.save();
const friendNew = {
  firstName: "Alice",
  lastName: "Parker",
};
People.findOneAndUpdate(
  { name: "Yash Salvi" },
  { $push: { friends: friendNew } },
  function (error, success) {
    if (error) {
      console.log(error);
    } else {
      console.log(success);
    }
  }
);

But I noticed that only first friend (i.e. Johhny Johnson) gets saved and the objective to push array element in existing array of "friends" doesn't seem to work as when I run the code , in database in only shows "First friend" and "friends" array has only one element ! So the simple solution is written below

const peopleSchema = new mongoose.Schema({
  name: String,
  friends: [
    {
      firstName: String,
      lastName: String,
    },
  ],
});
const People = mongoose.model("person", peopleSchema);
const first = new Note({
  name: "Yash Salvi",
  notes: [
    {
      firstName: "Johnny",
      lastName: "Johnson",
    },
  ],
});
first.save();
const friendNew = {
  firstName: "Alice",
  lastName: "Parker",
};
People.findOneAndUpdate(
  { name: "Yash Salvi" },
  { $push: { friends: friendNew } },
  { upsert: true }
);

Adding "{ upsert: true }" solved problem in my case and once code is saved and I run it , I see that "friends" array now has 2 elements ! The upsert = true option creates the object if it doesn't exist. default is set to false.

if it doesn't work use below snippet

People.findOneAndUpdate(
  { name: "Yash Salvi" },
  { $push: { friends: friendNew } },
).exec();