This should include MongoDB Compass.

Compass is a GUI, or graphical user interface, that simply provides a platform to view your data without the initial need for knowing MongoDB query syntax.

This makes it a great place to start!

MongoDB Overview

  • document database (NoSQL)
  • horizontal sharding => can theoretically serve trillions of records
  • uses JavaScript for data definition and manipulation
  • built-in map-reduce for dynamic collections
  • indexing on fields by value or free-text search

"Mongo is not a toy, although it can be fun to play with." - Josh Burke

Lab: Exploring with Compass

This is MongoDb's GUI tool. Let's open it up and see what it can do!

  • Open Compass and click on the green "Connect" button; it defaults to localhost for ease of use.


  • Look for the database named test** in the left side nav bar, and open it
  • Create a new collection
  • In the collection you just created try running through all the CRUD functions
    • Add some documents, update them, delete them...

** test is a default database name provided by MongoDB.

Concept: Database

to connect to a database you need a Mongo URI (or URL) identifying the server, port, etc.:

Connection URL format:

mongodb://username:[email protected]/database

for example


or (locally)


If no database with the provided name is given, it will default to test. Note that the term "database" is overloaded: it refers to either:

  1. a single MongoDB process hosting many data sets
  2. a single MongoDB data set containing many related collections

Concept: Collection

A collection holds documents.

Many collections can live in a database.

This is analogous to a table in SQL.

Concept: Document

In MongoDB, a document is essentially a single JavaScript object

Like in a relational database, a document can be created, read, updated, deleted, indexed, searched for, ...

Unlike in a relational database, a document can contain any value for its fields, including arrays and nested objects.

This nesting and type-flexibility makes it very appropriate to store whatever JavaScript objects your app uses, without needing to devise a mapping between nested objects and joined relational tables.


  • MongoDB has its own query syntax that, while very similar to JavaScript at times, has its own rules and structure!

This allows MongoDB to be used with a number of languages through the use of drivers, which are language-specific! For our case, we'll be using MongoDB's Node.js driver, because we're JavaScript people, and we're working server side.

Full list of drivers

Lab: Do it with JavaScript!

Let's make our first Mongo collection!

We will insert a document into a collection that lives in a database.

Start by making new directory, and initializing it as an npm repository and installing the mongodb drivers.

mkdir mongo_example
cd mongo_example
npm init -y
npm install mongodb

Do it with JavaScript! cont.

Next, create a file called mongoClient.js

This is where we'll configure the client, or the software that connects to the server

The server, in this case, is localhost:27017

in mongoClient.js, add:

const { MongoClient } = require("mongodb");
const uri = "mongodb://localhost:27017" //mongodb connects to port 27017 by default
const client = new MongoClient(uri)

Do it with JavaScript! cont.

Now, connect to the database library, and insert a document into the books collection

Let's do this with an asynchronous function so we can harness the await keyword and keep things in order

like so:

async function run() {

    await client.connect()
    const database = client.db('library')
    const collection = database.collection('books')
    await collection.insertOne({ title: "Eloquent Javascript", author: "Marijn Haverbeke" })
    await client.close()


Note: This is a bare-bones example that does nothing for error handling. It is simply meant to demonstrate the most basic data flow.

View it in Compass

Select the database and collection on the side and...


Voila! But what's that _id thing?

Concept: ObjectId

  • _id is assigned by Mongo when a document is inserted
  • ObjectId is a factory function that either generates a new id, or transforms a given string into a Mongo ID object