How to update subdocument with findOneAndUpdate in Mongoose?

In Mongoose, the findOneAndUpdate method is used to update data within MongoDB documents. When updating nested documents (i.e., documents embedded within a document), it is crucial to carefully specify the path for the target document.

Suppose we have a model named User that includes an array field called addresses, where each array item is an object containing street, city, and zip code. Our goal is to update a specific address for a particular user.

Step 1: Define the Model

First, we need to define the model:

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

const addressSchema = new Schema({
  street: String,
  city: String,
  zipCode: String
});

const userSchema = new Schema({
  name: String,
  addresses: [addressSchema]
});

const User = mongoose.model('User', userSchema);

Step 2: Using findOneAndUpdate to Update Nested Documents

To update data in nested documents, we must use MongoDB's dot notation to specify the field path for the update. Assume we know the _id of the address to modify.

javascript
const userId = 'some_user_id';
const addressId = 'some_address_id';
const newStreet = 'new_street_name';
const newCity = 'new_city_name';
const newZipCode = 'new_zip_code';

User.findOneAndUpdate(
  { _id: userId, 'addresses._id': addressId },
  {
    $set: {
      'addresses.$.street': newStreet,
      'addresses.$.city': newCity,
      'addresses.$.zipCode': newZipCode
    }
  },
  { new: true }  // Returns the updated document
)
.then(updatedDocument => {
  console.log('Update successful:', updatedDocument);
})
.catch(error => {
  console.error('Update failed:', error);
});

In this example:

• We use the first parameter of findOneAndUpdate to locate the correct user document while ensuring the addresses array contains an address with the matching _id.
• The $set operator updates specific fields within the nested document.
• 'addresses.$' serves as MongoDB's position placeholder, indicating the first element that satisfies the array query condition.
• The { new: true } option guarantees that the updated document is returned.

By employing this approach, we can precisely update the nested document within the array without impacting other nested documents.