How does module.superModule work and when would you use it?

module.superModule is a B2C Commerce mechanism that loads the same-named module from the next cartridge down in the cartridge path. It enables model inheritance without copying and forking code.

A typical use case:

1. SFRA provides app_storefront_base/cartridge/models/product/fullProduct.js with standard product properties
2. Your custom cartridge creates app_custom/cartridge/models/product/fullProduct.js
3. At the top of your file: var base = module.superModule; then base.call(this, product, options); to inherit the base model
4. You then add extra properties (e.g., loyalty points, subscription flag) to this

Without module.superModule, you would have to copy the entire base file and maintain it separately through every SFRA upgrade — a major maintenance burden. Using superModule keeps customisations upgrade-safe.