MongoDB Insert

MongoDB Insert in Node.js: insertOne() and insertMany()

Inserting records into a MongoDB collection in Node.js uses collection.insertOne() for a single document and collection.insertMany() for batches. If a document omits _id, the MongoDB Node.js driver generates a unique ObjectId automatically and returns insertedId (or insertedIds) so you can link related data right away.

Inserting Single Documents and Bulk Batches

Always attach timestamps (createdAt: new Date()) explicitly in Node.js and handle duplicate-key errors (err.code === 11000) when inserting into collections with unique indexes.

import { MongoClient } from 'mongodb';

const client = new MongoClient(process.env.MONGODB_URI || 'mongodb://127.0.0.1:27017');

async function seedProducts() {
  try {
    await client.connect();
    const products = client.db('kodersolution_store').collection('products');

    const single = await products.insertOne({
      sku: 'KB-101',
      name: 'Wireless Mechanical Keyboard',
      price: 89.99,
      tags: ['peripherals', 'keyboard'],
      createdAt: new Date(),
    });
    console.log('Inserted ID:', single.insertedId);

    const batch = await products.insertMany(
      [
        { sku: 'MS-202', name: 'Ergonomic Mouse', price: 49.0, createdAt: new Date() },
        { sku: 'HB-303', name: 'USB-C Hub', price: 34.5, createdAt: new Date() },
      ],
      { ordered: false }
    );
    console.log('Batch inserted count:', batch.insertedCount);
  } catch (err) {
    if (err.code === 11000) {
      console.error('Duplicate SKU skipped or rejected.');
    } else {
      throw err;
    }
  } finally {
    await client.close();
  }
}

seedProducts().catch(console.error);

Understanding { ordered: true } vs { ordered: false }

By default, insertMany() runs with { ordered: true }, stopping immediately at the first error and skipping remaining documents in the array. Passing { ordered: false } tells MongoDB to continue inserting all other valid documents even if one item fails a unique index check.

Common Mistakes to Avoid

• Inserting 10,000 rows in a for loop with await insertOne(): Sequential network round-trips make bulk imports painfully slow. Batch arrays in chunks of 500–1,000 documents using insertMany().
• Passing raw req.body directly into insertOne(req.body): Users could inject unexpected fields like role: 'admin' or isPaid: true. Destructure only allowed fields explicitly before inserting.
• Using deprecated insert() method: Modern mongodb v4+ drivers removed collection.insert(); always use insertOne() or insertMany().

Frequently Asked Questions

What does insertOne() return in the modern Node.js driver?

It returns { acknowledged: true, insertedId: ObjectId(...) } rather than the full inserted document.

Can I provide my own custom _id value?

Yes. Passing _id: 'order-2026-001' or a UUID string works fine as long as every _id in that collection remains unique.

What is the maximum size of a single MongoDB document?

Each BSON document can be up to 16 MB. Store large files in S3 or MongoDB GridFS instead of embedding giant binary blobs inside documents.