timreynolds / js-domain

Base classes and ts declarations for using the domain model pattern with DDD in js

JS DDD Classes

A set of base classes used to implement DDD style domain model pattern in JavaScript.

Classes

Below outlines the classes provided in this package and the functionality encapsulated in each.

Value Object

Objects that matter only as the combination of their attributes. Two value objects with the same values for all their attributes are considered equal.

Provides a createdOn date which is can either be set via the constructor or defaults to Moment utc.

Entity

Objects that have a distinct identity that runs through time and different representations.

Extends ValueObject but provides an id to distinguishes the objects identity throughout time. Defaulted to a v4 GUID when not provided.

Aggregate Root

Cluster of domain objects that can be treated as a single unit and the basic element of transfer of data storage.

Extends Entity with the additional responsibility of tracking and queuing Events.

Within these classes the Aggregate takes responsibility for eventing for any entity it manages. Events are stored within the class and made accessible vis the enqueuedEvents method. The advantages of this approach are;

• Class isn't coupled to a publisher
• Events can be batched processed
• Events can be encapsulated within a transactional boundary

Event

Captures the memory of something interesting which affects the domain

Used to provide a consistent interface for events from the domain expecting a type and data properties via the constructor. The following common event properties are default unless provided;

• id
• correlationId
• raisedOn

Intended to be extended by specific event classes that include data validation.

#Example Usage

All classes are exposed at root level.

const { ValueObject } = require('@reynolds/domain');
class Example extends ValueObject {

As are typescript declarations

const { ICreatedOn } = require('@reynolds/domain');
class Example implements ICreatedOn {}