Overview

EQuateJS loosely implements CQRS/ES - or the more modern Flux - architecture for building backend web APIs. Here's how it works.

Core Building Blocks

The core building blocks are:

• commands in the form of events that update the application state
• queries return the current state of the application

The core API provides an ability to register handlers for events and queries but - more importantly - it also allows adding new registrars.

• registrars are layers of abstractions that map to sets of events or queries

Default Registrars

While events and queries by itself are already powerful, sometimes you'll run into issues of polluting your events from unintentionally providing it with more context.

For example, in express, your typical req object usually gets populated with additional context like req.user as it goes down the middleware chain.

With actions and views, the request message is separated from the technical contexts and handlers are provided via the register API to map those into events and queries.

• actions are higher level abstractions that allow mapping of user intentions and contexts to events
• views applies the same context mapping for queries

References

For a comprehensive introduction to CQRS/ES and Flux, check out the following links:

• CQRS
• Event Sourcing
• Reference 3: Introducing Event Sourcing
• Flux Architecture