Gurkirat Singh

Posted on Apr 10, 2020

Pocket Guide on Mongoose ODM for NodeJS

#mongodb #mongoose #node #odm

Course Overview

Prerequisite Knowledge

Basics of NodeJS

What you will learn in this course

In this, you will learn about the NoSQL database, whose subtle introduction was given in the sequelize's course. Also, you will learn the basics of MongoDB, the leading NoSQL DB support provider and the Mongoose ODM developed my Automattic

Project

The project is in project directory

NOTE: This course is made with jupyter notebook. If you want the notebook drop a message at tbhaxor@gmail.com. I will be adding more topics under misc, so make sure you subscribe to the repository.

What is NoSQL Database

NoSQL database is a type of database that doesn’t follow the approach that SQL follows. It uses different query language and the document doesn’t have to stick to the same schema. The records in it have no relations, duplication of data is preferred

The database contains collections, collections contains documents. These documents are the records. It stores the data in binary JSON (called bson)

What is MongoDB

MongoDB is a NoSQL database service provided by the company named MongoDB. It is specially built for large scale applications, that may store lots and lots of data.

The documents within documents are known as embedded documents. MongoDB uses this way to duplicate the document. Another concept of linking other documents is called references, where the unique id (in MongoDB it's called object id and denoted by _id) of the document is added in the document

Embedded Document way

{
    "_id": "id1",
    "name": "Gurkirat Singh",
    "age": 22,
    "address": {
        "state": "Rajasthan",
        "country": "India"
    }
}

Now the referencing approach needs two separate documents of address and user

Address Document

{
    "_id": "id2",
    "state": "Rajasthan",
    "country": "India"
}

User Document

{
    "_id": "id1",
    "name": "Gurkirat Singh",
    "age": 22,
    "address": "id2"
}

Setting up MongoDB

Installing on Windows: Documentation | Video

Installing on Linux: Documentation | Video

Or you can use MongoDB Atlas. Learn how to set up the cluster from this video → https://www.youtube.com/watch?v=YZ66YqGPip8

Installing MongoDB Compass

Visit the link → https://docs.mongodb.com/compass/current/install/
Select the OS
Follow the instructions on the page.

After installing compass, follow the instructions from the docs to connect it with your MongoDB instance

Installing MongoDB Driver for NodeJS

# using yarn
yarn add mongodb

# using npm
npm i mongodb

const { MongoClient } = require("mongodb")

After this, you can connect to the MongoDB server by MongoClient.connect() method. It requires a connection string with the following syntax

mongodb://[user:password]@hostname[:port]/database

The data in [ ] are optional. Since I am using MongoDB on my localhost with test db, therefore the connection string in my case will be

mongodb://localhost/test

let db = null;

MongoClient.connect("mongodb://localhost/test", {
    useUnifiedTopology: true // recommended by mongoclient
}).then(client => {
    db = client.db() // getting the object of database
    console.log("Connected to the DB")
}).catch(e => console.warn(e))

Connected to the DB

CRUD Operations on the database

CREATE Document

db.collection("users").insertOne({name: "Gurkirat", age: 22})
    .then(response => console.log(response.result))
    .catch(console.warn)

{ n: 1, ok: 1 }

Creating Document in Bulk

let users = [
    { name:"Amit", age: 20 }, 
    { name:"John", age: 25 }
]

db.collection("users").insertMany(users)
    .then(response => console.log(response.result))
    .catch(console.warn)

{ ok: 1, n: 2 }

READ Document

db.collection("users").find().toArray().then(r => {
    console.log(r)
}).catch(console.warn)

[
  { _id: 5e89a3c678852a72f87479f8, name: 'Gurkirat', age: 22 },
  { _id: 5e89a46778852a72f87479f9, name: 'Amit', age: 20 },
  { _id: 5e89a46778852a72f87479fa, name: 'John', age: 25 }
]

Did you see the new field _id. It is an auto generated he 12-byte value called ObjectId. It consists of:

a 4-byte timestamp value, representing the ObjectId’s creation, measured in seconds since the Unix epoch
a 5-byte random value
a 3-byte incrementing counter, initialized to a random value

Fetching Single Record

db.collection("users").find({ name: "John" }).next()
    .then(r => console.log(r))
    .catch(console.warn)

{ _id: 5e89a46778852a72f87479fa, name: 'John', age: 25 }

Fetching Record by ObjectID

You can compare the ObjectID with string

const { ObjectId }  = require("mongodb")

db.collection("users").find({ "_id": ObjectId("5e89a3c678852a72f87479f8") }).next()
    .then(r => console.log(r))
    .catch(console.warn)

{ _id: 5e89a3c678852a72f87479f8, name: 'Gurkirat', age: 22 }

UPDATE Document

db.collection("users").updateOne({ "_id": ObjectId("5e89a3c678852a72f87479f8") }, {$set: { name: "Gurkirat Singh" }})
    .then(r => console.log(r.result))
    .catch(console.warn)

{ n: 1, nModified: 0, ok: 1 }

db.collection("users").find({ "_id": ObjectId("5e89a3c678852a72f87479f8") }).next()
    .then(r => console.log(r))
    .catch(console.warn)

{ _id: 5e89a3c678852a72f87479f8, name: 'Gurkirat Singh', age: 22 }

DELETE Document

db.collection("users").deleteOne({ "_id": ObjectId("5e89a3c678852a72f87479f8") })
    .then(r => console.log(r.result))
    .catch(console.warn)

{ n: 1, ok: 1 }

db.collection("users").find().toArray().then(r => {
    console.log(r)
}).catch(console.warn)

[
  { _id: 5e89a46778852a72f87479f9, name: 'Amit', age: 20 },
  { _id: 5e89a46778852a72f87479fa, name: 'John', age: 25 }
]

Adding References

db.collection("users").findOne().then(r => {
    db.collection("products").insertOne({
        title: "A book to ODM in Nodejs",
        price: 200.99,
        added_by: r._id
    })
        .then(r => console.log(r.result))
        .catch(console.warn)
}).catch(console.warn)

{ n: 1, ok: 1 }

db.collection("products").find().toArray()
    .then(console.log)
    .catch(console.warn)

[
  {
    _id: 5e89ca3d78852a72f87479fb,
    title: 'A book to ODM in Nodejs',
    price: 200.99,
    added_by: 5e89a46778852a72f87479f9
  }
]

Populating the User Data

db.collection("products").find().next()
    .then(r => {
        console.log("Book Title:", r.title)
        console.log("Price of Book:", r.price)
        db.collection("users").find({ _id: r.added_by }).next()
            .then(r => {
                console.log("Added By:", r.name)
            })
            .catch(console.warn)
    })
    .catch(console.warn)

Book Title: A book to ODM in Nodejs
Price of Book: 200.99
Added By: Amit

Mongoose: MongoDB ODM

Mongoose is an Object Document Mapping library for MongoDB in nodejs. This helps the nodejs developer to focus on data more than dealing with MongoDB. It allows the developers to define models with which they can interact with the database.

Installing Mongoose

# using npm
npm i mongoose

# using yarn
yarn add mongoose

const mongoose = require("mongoose")

Connecting to the DB

mongoose.connect("mongodb://localhost/test", {
    // settings are recommended by mongoose
    useUnifiedTopology: true, 
    useNewUrlParser: true,
    useFindAndModify: false
}).then(() => {
    console.log("Connected to DB")
}).catch(console.warn)

Connected to DB

Creating Product Schema and Model

const {Schema, model} = require("mongoose")

const ProductSchema = new Schema({
    title: String,
    price: Number,
    added_by: { type: Schema.Types.ObjectId, ref: "User" } // adding reference to User model via _id field
})

const Product = model("Product", ProductSchema)

Creating User Schema and Model

const UserSchema = new Schema({
    name: String,
    email: String,
})

const User = model("User", UserSchema)

Performing CRUD Operations

CREATE

let newProduct = new Product()
let newUser = new User()


newUser.name = "Dummy User"
newUser.email = "dummy@user.com"

newProduct.title = "A book on C Plus Plus";
newProduct.price = 200.99;
newProduct.added_by = newUser._id;

5e89d1db8ccb5891c7c1d522

newUser.save().then(r => {
    console.log("Added to new User to DB");
}).catch(console.warn)

Added to new User to DB

newProduct.save().then(r => {
    console.log("Added to new Product to DB");
}).catch(console.warn)

Added to new Product to DB

READ all the Data

User.find().then(r => {
    console.log(r)
}).catch(console.warn)

[
  {
    _id: 5e89d1db8ccb5891c7c1d522,
    name: 'Dummy User',
    email: 'dummy@user.com',
    __v: 0
  }
]

Product.find().then(r => {
    console.log(r)
}).catch(console.warn)

[
  {
    _id: 5e89d1db8ccb5891c7c1d521,
    title: 'A book on C Plus Plus',
    price: 200.99,
    added_by: 5e89d1db8ccb5891c7c1d522,
    __v: 0
  }
]

Populating the Reference

Product.find().populate("added_by").then(r => {
    console.log(r)
}).catch(console.warn)

[
  {
    _id: 5e89d1db8ccb5891c7c1d521,
    title: 'A book on C Plus Plus',
    price: 200.99,
    added_by: {
      _id: 5e89d1db8ccb5891c7c1d522,
      name: 'Dummy User',
      email: 'dummy@user.com',
      __v: 0
    },
    __v: 0
  }
]

Populating the Reference and Projecting Specific Fields Only

Product.find().populate("added_by", {name: true}).then(r => {
    console.log(r)
}).catch(console.warn)

[
  {
    _id: 5e89d1db8ccb5891c7c1d521,
    title: 'A book on C Plus Plus',
    price: 200.99,
    added_by: { _id: 5e89d1db8ccb5891c7c1d522, name: 'Dummy User' },
    __v: 0
  }
]

Finding By _id

Product.findById("5e89d1db8ccb5891c7c1d521")
    .then(r => console.log(r))
    .catch(console.warn)

{
  _id: 5e89d1db8ccb5891c7c1d521,
  title: 'A book on C Plus Plus',
  price: 200.99,
  added_by: 5e89d1db8ccb5891c7c1d522,
  __v: 0
}

Fetch Single Result by non _id Field

Product.findOne({ price: { $gte: 100 } }) // finding one product whose price is greater than equal to 100
    .then(r => console.log(r))
    .catch(console.warn)

{
  _id: 5e89d01526491f916866e730,
  title: 'A book on C Plus Plus',
  price: 200.99,
  added_by: 5e89d01526491f916866e731,
  __v: 0
}

UPDATE the Document

Product.findByIdAndUpdate("5e89d1db8ccb5891c7c1d521", { title:"C++ book" })
    .then(r => console.log(r))
    .catch(console.warn)

{
  _id: 5e89d1db8ccb5891c7c1d521,
  title: 'A book on C Plus Plus',
  price: 200.99,
  added_by: 5e89d1db8ccb5891c7c1d522,
  __v: 0
}

You can also use the updateOne method to update the document.

Product.findById("5e89d1db8ccb5891c7c1d521")
    .then(r => console.log(r))
    .catch(console.warn)

{
  _id: 5e89d1db8ccb5891c7c1d521,
  title: 'C++ book',
  price: 200.99,
  added_by: 5e89d1db8ccb5891c7c1d522,
  __v: 0
}

DELETE the Document

Product.findByIdAndDelete("5e89d1db8ccb5891c7c1d521")
    .then(r => console.log(r))
    .catch(console.warn)

{
  _id: 5e89d1db8ccb5891c7c1d521,
  title: 'C++ book',
  price: 200.99,
  added_by: 5e89d1db8ccb5891c7c1d522,
  __v: 0
}

You can also use the deleteOne method to delete the document

Product.findById("5e89d1db8ccb5891c7c1d521")
    .then(r => console.log(r))
    .catch(console.warn)

null

To learn more on mongoose, follow this link to the documentation → https://mongoosejs.com/docs/guide.html

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