aggregation.js

const { MongoClient } = require('mongodb');

async function main() {
    /**
     * Connection URI. Update <username>, <password>, and <your-cluster-url> to reflect your cluster.
     * See https://docs.mongodb.com/drivers/node/ for more details
     */
    const uri = "mongodb+srv://<username>:<password>@<your-cluster-url>/sample_airbnb?retryWrites=true&w=majority";

    /**
     * The Mongo Client you will use to interact with your database
     * See https://mongodb.github.io/node-mongodb-native/3.6/api/MongoClient.html for more details
     * In case: '[MONGODB DRIVER] Warning: Current Server Discovery and Monitoring engine is deprecated...'
     * pass option { useUnifiedTopology: true } to the MongoClient constructor.
     * const client =  new MongoClient(uri, {useUnifiedTopology: true})
     */
    const client = new MongoClient(uri);

    try {
        // Connect to the MongoDB cluster
        await client.connect();

        // Make the appropriate DB calls

        // Print the 10 cheapest suburbs in the Sydney, Australia market
        await printCheapestSuburbs(client, "Australia", "Sydney", 10);

    } finally {
        // Close the connection to the MongoDB cluster
        await client.close();
    }
}

main().catch(console.error);

/**
 * Print the cheapest suburbs for a given market
 * @param {MongoClient} client A MongoClient that is connected to a cluster with the sample_airbnb database
 * @param {String} country The country for the given market
 * @param {String} market The market you want to search
 * @param {number} maxNumberToPrint The maximum number of suburbs to print
 */
async function printCheapestSuburbs(client, country, market, maxNumberToPrint) {
    const pipeline = [
        {
            '$match': {
                'bedrooms': 1,
                'address.country': country,
                'address.market': market,
                'address.suburb': {
                    '$exists': 1,
                    '$ne': ''
                },
                'room_type': 'Entire home/apt'
            }
        }, {
            '$group': {
                '_id': '$address.suburb',
                'averagePrice': {
                    '$avg': '$price'
                }
            }
        }, {
            '$sort': {
                'averagePrice': 1
            }
        }, {
            '$limit': maxNumberToPrint
        }
    ];

    // See https://mongodb.github.io/node-mongodb-native/3.6/api/Collection.html#aggregate for the aggregate() docs
    const aggCursor = client.db("sample_airbnb").collection("listingsAndReviews").aggregate(pipeline);

    await aggCursor.forEach(airbnbListing => {
        console.log(`${airbnbListing._id}: ${airbnbListing.averagePrice}`);
    });
}