What is the Universal Signature enforced by this skill?

It requires all factory functions to follow a specific two-argument structure: the first argument is always the resource or dependencies, and the second is optional configuration specific to that factory.

What is a common anti-pattern this skill solves?

It prevents 'Mixed Options Bloat,' where client-level configurations (like timeouts) are passed into method-level calls, leading to confusing and brittle APIs.

How does this skill improve unit testing?

By passing dependencies as arguments rather than creating them inside functions, it allows developers to easily inject mock clients or stubs during testing without modifying the function logic.

Can I use this for services with multiple dependencies?

Yes, the pattern recommends passing a destructured object as the first argument when multiple clients (like a database, cache, and HTTP client) are required.

Factory Function Composition

Name: Factory Function Composition
Author: EpicenterHQ

byEpicenterHQ

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3,817

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API Development

Standardizes code architecture using factory patterns to achieve clean dependency injection and modular service composition.

This skill provides a standardized framework for implementing factory function patterns in TypeScript, ensuring a strict separation between client, service, and method-level configurations. By enforcing a universal signature for dependencies and options, it eliminates common anti-patterns like hidden client creation or mixed configuration blobs. This approach facilitates highly testable, modular, and maintainable codebases by ensuring that each layer of your application owns its specific configuration and dependencies.

Key Features

01Identifies and refactors anti-patterns like hidden resource creation within functions

02Promotes clean dependency injection for easier unit testing with mocks

03Enforces a universal two-argument factory signature for consistent API design

043,817 GitHub stars

05Supports scalable patterns for services requiring multiple external dependencies

06Separates client, service, and method configuration layers to prevent configuration leakage

Use Cases

01Refactoring legacy functions that mix business logic with client initialization

02Structuring backend services for high testability via dependency injection

03Designing modular API client libraries with clear separation of concerns

What are Skills?·How to Install

Install with 🐟 Skill.Fish

npx skillfish add epicenterhq/epicenter factory-function-composition

For use in Claude.ai and ChatGPT

Download Skill