Connecting to MongoDB

Establish database connnection using the Node.js driver:

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

const databaseUrl = 'mongodb://localhost:27017';
const client = new MongoClient(databaseUrl);

async function connectToDatabase() {
    try {
        await client.connect();
        console.log('Database connection established');
        return client.db('sample_database');
    } catch (connectionError) {
        console.error('Connection failed:', connectionError);
        throw connectionError;
    }
}

Selecting Target Collection

Access the specific collection for querying:

const targetCollection = database.collection('sales_data');

Aggregation Pipeline for Sum Calculation

Execute agrgegation pipeline to compute field summation:

async function calculateFieldSum(collection, fieldName) {
    try {
        const pipeline = [
            {
                $group: {
                    _id: null,
                    aggregateSum: { $sum: `$${fieldName}` }
                }
            }
        ];
        
        const aggregationResult = await collection.aggregate(pipeline).toArray();
        return aggregationResult[0]?.aggregateSum || 0;
    } catch (aggregationError) {
        console.error('Aggregation operation failed:', aggregationError);
        throw aggregationError;
    }
}

// Usage example
connectToDatabase()
    .then(db => {
        const dataCollection = db.collection('transactions');
        return calculateFieldSum(dataCollection, 'amount');
    })
    .then(sumResult => {
        console.log(`Total sum: ${sumResult}`);
    })
    .catch(error => {
        console.error('Operation error:', error);
    });