According to SFRA best practices, what is the correct approach to improve code reusability in a custom controller?

Using the superModule property in existing routes to extend their functionality is a best practice in Salesforce B2C Commerce architecture. This approach allows developers to build on existing functionality while promoting code reusability. By utilizing superModule, developers can create custom behaviors or modify default behaviors without rewriting the entire route code. This ensures that changes can be made in a modular fashion, enhancing maintainability and reducing redundancy.

The benefits of this approach include easier updates to the core codebase and minimized risk of introducing bugs when extending functionality. It helps in creating a clear hierarchy where custom code can efficiently extend the existing logic rather than duplicating it. Thus, the superModule property is aligned well with the principles of code reuse and scalability in SFRA.

In contrast, other options present less effective methods for achieving code reusability. For instance, defining a middleware function may introduce new routes but does not inherently promote the reuse of existing logic. Appending functions to all existing routes can clutter and complicate the codebase, making it harder to manage. Simply creating a new controller in a separate cartridge and replacing existing routes can lead to more work and does not allow for the leveraging of already established functionality. Therefore, using the superModule property is the most efficient and recommended way