• Unidirectional rendering frameworks have given developers the ability to modularise code bases.
  • The prevailing methodology seems to be small dumb components and large smart components.
  • This split is too naive and in practice it doesn't create a meaningful abstraction. Codebases end up with a tiny amount of small reusable 'dumb' components and a large amount of monolithic application specific 'smart' components.

What the front-end really needs is a way to talk about interfaces that effectively separates its concerns.

Core Ideas

Moose aims to provide clear descriptions of the parts that make up a client-side application. If we can describe these parts correctly it becomes easy to label and categorise the areas of our apps. Once categorised, code structure and responsibility becomes easier to define.

Clientside Concerns

The client side code has six clear areas of concern:

  • Data fetching
  • Data Storage
  • Application logic
  • User Interaction Logic
  • Positional Styles (Layout)
  • Aesthetic Styles (Component Styles)

_Broadly speaking you can split these six areas of concern into two main layers. Application and Interaction. Application is concerned with data and how it is stored and transformed to render. Interaction is concerned with how things look and feel and how the user interacts with them.

The interaction layer is general and naturally lends itself to abstraction. The application layer is specific and tends to describe concrete implementations._

Application Layer

Data Fetching

This concern describes how data from exterior sources makes it's way into the application.

Data Storage

Often labelled as state management, data storage describes how external data is stored in memory throughout your app.

Application Logic

Like business logic in a backend, application logic is the specific ways that data is transformed and applied to your interfaces. Taking a collection of users and applying their attributes to a table is application logic. In a unique location you have decided that these users are best displayed as a table and this is how you transform the data into the shape a table requires.

Interaction Layer

Interaction Logic

Distinct to application logic, interaction logic is the specific ways the user interacts with parts of the site. When a user types in a search box and a list of possible choices appears, that is interaction logic. Some part of the app is concerned with what the user has typed and what possible choices it could show in response. It is a separate concern from application logic because it doesn't care what data it is given or where it came from, just how that data should respond to the users interaction.

Aesthetic Styles

Aesthetic styles describe how your individual components should look. Libraries and methodologies, like Bootstrap, Atomic Design etc. have got this right. You can describe all possible states of a button quite clearly and all the code required to define how a button looks should be separate from other parts of your app.

Positional Styles

Positional styles describe how the different parts of your app relate to each other in position. Grids, floats, text spacing all fall under this category. Component libraries often become bloated and confused when positional styles are combined with aesthetic ones. Class names like .marginLeftLarge and paddingTopExtraSmall become littered throughout the app, making things hard to move and refactor. Positional styles are a unique concern and should be separate for other parts of you app.

Allan Hortle


  • EntyNormalized state management
  • FronadsMonads with beginner-friendly naming
  • MooseFront-end Methodology