The idea of this repo is to show how to perform Subdocument array mutation operations using NodeJs and MongoDb + Mongoose ORM.

The document database is designed to store high volume application data. The application needs to manage an array of objects (i.e. posts, mentions) which get stored as properties of a root JSON document.

• We have Content Creators responsible for creating social posts and attach mentions to them.

• Both "posts" and "mentions" are subdocument arrays because they are made up of objects each having their own _id

• Subdocument arrays can be nested as shown with the "mentions" structure under an individual "post".

Example structure:

{
  _id: 1,
  name: 'Johnny Content Creator',
  posts: [
    {
      _id: 2,
      value: 'one',
      mentions: []
    },
    {
      _id: 3,
      value: 'two',
      mentions: [
        {
          _id: 5,
          text: 'apple'
        },
        {
          _id: 6,
          text: 'orange'
        }
      ]
    },
    {
      _id: 4,
      value: 'three',
      mentions: []
    }
  ]
}

The document database we are using supports the following operations for subdocument arrays:

• $add: adding new subdocument to the end of an array
• $update: updating specific subdocuments by index (zero-based)
• $remove: removing specific subdocuments by index (zero-based)

//INPUT: Add post
{ 
  posts: [
    {
      value: 'four'
    }
  ]
}

//OUTPUT: Add post
{
  $add: {
    posts: [
      {
        value: 'four'
      }
    ]
  }
}

//INPUT: Update value field of post with _id of 2
{ 
  posts: [
    {
      _id: 2,
      value: 'too'
    }
  ]
}

//OUTPUT: Update value field of post at index 0
{ 
  $update: {
    'posts.0.value': 'too'
  }
}

//INPUT: Remove post with _id of 2
{
  posts: [
    {
      _id: 2,
      _delete: true
    }
  ]
}
//OUTPUT: Remove post at index 0
{ 
  $remove : {
    'posts.0' : true
  }
}

Node.js version 10.19.0

• Node.js.

NPM version 6.13.4

• npm.

mongoDB version 3.6

• mongoDB.

# cd to root folder
npm install

npm start

# Run all tests
npm test

# Run unit tests
npm run test:unit

# Run unit tests
npm run test:integration

npm run test:report

• Creators