To make MongoDB database manipulation easy, we can use the Mongoose NPM package to make working with MongoDB databases easier.

In this article, we’ll look at how to use Mongoose to manipulate our MongoDB database.

Discriminators

Discriminators are a schema inheritance mechanism.

They let us enable multiple models to have overlapping schemas on top of the same MongoDB collection.

For example, we can use them as follows:

async function run() {
  const { createConnection, Types, Schema } = require('mongoose');
  const db = createConnection('mongodb://localhost:27017/test');
  const options = { discriminatorKey: 'kind' };
  const eventSchema = new Schema({ time: Date }, options);
  const Event = db.model('Event', eventSchema);
  const ClickedLinkEvent = Event.discriminator('ClickedLink',
    new Schema({ url: String }, options));
  const genericEvent = new Event({ time: Date.now(), url: 'mongodb.com' });
  console.log(genericEvent)
  const clickedEvent =
    new ClickedLinkEvent({ time: Date.now(), url: 'mongodb.com' });
  console.log(clickedEvent)
}
run();

We created an Event model from the eventSchema .

It has the discriminatorKey so that we get can discriminate between the 2 documents we create later.

To create the ClickedLinkEvent model, we call Event.discriminator to create a model by inheriting from the Event schema.

We add the url field to the ClickedLinkEvent model.

Then when we add the url to the Event document and the ClickedLinkEvent document, only the clickedEvent object has the url property.

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