How to use MongoDB with Node.js

If you are unfamiliar with MongoDB check our guide on its basics and on how to install and use it :) If you know SQL and want the differences, read How MongoDB is different from a SQL database.

We’ll be using the official mongodb npm package (examples checked against mongodb@7.6.0). If you already have a Node.js project you are working on, install it using

npm install mongodb

If you start from scratch, create a new folder with your terminal and run npm init -y to start up a new Node.js project, and then run the npm install mongodb command.

Connecting to MongoDB

Import MongoClient from the mongodb package:

const { MongoClient } = require('mongodb')

Create a URL to the MongoDB server. If you use MongoDB locally, the URL will be something like mongodb://localhost:27017, as 27017 is the default port.

const url = 'mongodb://localhost:27017'

Create a client, then await connect(). You don’t need the old useNewUrlParser / useUnifiedTopology options any more:

const client = new MongoClient(url)

async function main() {
  try {
    await client.connect()
    //...
  } finally {
    await client.close()
  }
}

main()

Now you can select a database using the client.db() method:

const db = client.db('kennel')

Create and get a collection

You can get a collection by using the db.collection() method. If the collection does not exist yet, it’s created.

const collection = db.collection('dogs')

Insert data into a collection a Document

Add to app.js the following which uses the insertOne() method to add an object to the dogs collection:

const result = await collection.insertOne({ name: 'Roger' })
console.log(result.insertedId)

You can add multiple items using insertMany(), passing an array as the first parameter:

const result = await collection.insertMany([
  { name: 'Togo' },
  { name: 'Syd' },
])
console.log(result.insertedCount)

Find all documents

Use the find() method on the collection to get all the documents added to the collection. find() returns a cursor, so call toArray():

const items = await collection.find().toArray()
console.log(items)

Find a specific document

Pass an object to the find() method to filter the collection based on what you need to retrieve:

const items = await collection.find({ name: 'Togo' }).toArray()
console.log(items)

If you know you are going to get one element, use findOne():

const item = await collection.findOne({ name: 'Togo' })
console.log(item)

Update an existing document

Use the updateOne() method to update a document:

const result = await collection.updateOne(
  { name: 'Togo' },
  { $set: { name: 'Togo2' } }
)
console.log(result.modifiedCount)

Delete a document

Use the deleteOne() method to delete a document:

const result = await collection.deleteOne({ name: 'Togo' })
console.log(result.deletedCount)

Closing the connection

Once you are done with the operations you can call the close() method on the client object:

await client.close()

In a long-running server you usually keep one MongoClient for the process lifetime and close it on shutdown. In a short script, wrap the work in try / finally and close in finally.

Use promises or async/await

The driver API is promise-based. Prefer async/await. You can also chain promises if you prefer:

collection
  .findOne({ name: 'Togo' })
  .then((item) => {
    console.log(item)
  })
  .catch((err) => {
    console.error(err)
  })

or async/await:

const find = async () => {
  try {
    const item = await collection.findOne({ name: 'Togo' })
    console.log(item)
  } catch (err) {
    console.error(err)
  }
}

find()

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