Multiple same schema nested objects with a dynamic name inside an object

Question

Is it possible to define a schema in a way that I can define only one key/value pair as a nested object and not having to repeat multiple pairs of just different keys with the same schema as a value.

From something like this:

const Nested = new mongoose.Schema(
  {
    name: String,
  }
);

const Main = new mongoose.Schema(
  {
    name: String,
    nested: {
      en: Nested,
      bg: Nested,
      fr: Nested,
      // etc...
    }
  }
);

To something like this:

...

const Main = new mongoose.Schema(
  {
    name: String,
    nested: {
      {somethingDynamic}: Nested
    }
  }
);

It's easy if nested can be an array, but it has to be an object.

Answer 1

The fields defined in the schema must be a limited set and predictable. A schema with infinite fields is meaningless and will cause an exception. The easy way is to create a schema builder function.

import mongoose from 'mongoose';
import { config } from '../../config';

mongoose.set('debug', true);
console.log(mongoose.version);

const Nested = new mongoose.Schema({
    name: String,
});

const nestedSchemaBuilder = (keys, schema) => {
    return keys.reduce((acc, key) => {
        acc[key] = schema;
        return acc;
    }, {});
};

const keys = ['en', 'bg', 'fr'];
const MainSchema = new mongoose.Schema({
    name: String,
    nested: nestedSchemaBuilder(keys, Nested),
});
const Main = mongoose.model('Main', MainSchema);

(async function main() {
    try {
        await mongoose.connect(config.MONGODB_URI);
        // seed
        await Main.create([
            {
                name: 'a',
                nested: keys.reduce((acc, cur) => {
                    acc[cur] = { name: cur };
                    return acc;
                }, {}),
            },
        ]);
        const doc = await Main.findOne();
        console.log(doc?.toObject());
    } catch (error) {
        console.error(error);
    } finally {
        await mongoose.connection.close();
    }
})();

Logs:

7.3.4
Mongoose: mains.insertOne({ name: 'a', nested: { en: { name: 'en', _id: ObjectId("64b12146362b767506a1a5c4") }, bg: { name: 'bg', _id: ObjectId("64b12146362b767506a1a5c5") }, fr: { name: 'fr', _id: ObjectId("64b12146362b767506a1a5c6") } }, _id: ObjectId("64b12146362b767506a1a5c3"), __v: 0}, {})
Mongoose: mains.findOne({}, {})
{
  nested: {
    en: { name: 'en', _id: new ObjectId("64b12146362b767506a1a5c4") },
    bg: { name: 'bg', _id: new ObjectId("64b12146362b767506a1a5c5") },
    fr: { name: 'fr', _id: new ObjectId("64b12146362b767506a1a5c6") }
  },
  _id: new ObjectId("64b12146362b767506a1a5c3"),
  name: 'a',
  __v: 0
}