How would you design a generic function that can handle such scenarios and be reused across platforms?

I would create a platform‑agnostic abstraction using interfaces or protocols. For example, in TypeScript I’d define an interface DataFetcher with a fetch() method that returns a Promise of a generic type T. Each platform (Node, browser, mobile) would implement this interface with its own HTTP client or SDK. I’d use dependency injection to supply the concrete implementation at runtime, allowing the same business logic to run anywhere. The function would be generic over T, so callers can specify the expected shape of the data. I’d also apply the Strategy pattern to swap out retry or caching strategies, and the Factory pattern to instantiate the correct fetcher based on environment variables. This design keeps the core logic platform‑agnostic, promotes testability, and reduces duplication.