Does this pattern impact application performance?

In modern V8 engines, the overhead of creating small objects for arguments and dependencies is negligible compared to I/O operations like database queries or network requests.

What is the fn(args, deps) pattern?

It is an architectural pattern that replaces traditional classes with functions where 'args' represents per-call input data and 'deps' contains injected long-lived infrastructure or collaborators.

What tools does this skill use for testing?

The skill integrates with Vitest and vitest-mock-extended to provide a standardized pattern for mocking injected dependencies in unit tests.

How does this skill handle existing frameworks like NestJS?

It promotes using classes as thin delegation wrappers for framework integration while keeping the core business logic in pure, testable functions.

Why use functions over classes for business logic?

Functions prevent the 'God Object' problem, make dependency bloat immediately visible, and eliminate implicit coupling caused by the 'this' keyword, leading to more maintainable code.

Functional Dependency Injection Pattern

Name: Functional Dependency Injection Pattern
Author: jagreehal

byjagreehal

0•

API開発

Enforces the fn(args, deps) architectural pattern to promote testability and maintainable code through explicit dependency injection.

This skill guides developers in implementing a functional alternative to class-based services by standardizing the fn(args, deps) signature. By separating per-call arguments from long-lived infrastructure dependencies, it prevents 'god object' bloat, simplifies unit testing with automatic mocking, and ensures architectural clarity in TypeScript applications. It provides specific guidance on factory functions, type-only imports, and maintaining framework-agnostic business logic even when using frameworks like NestJS.

主な機能

01Standardized fn(args, deps) function signatures

02Framework-agnostic business logic integration for NestJS and Express

03Strangler fig migration strategies for legacy class-based code

04Strict separation of per-call data and long-lived collaborators

05Automated dependency mocking patterns with vitest-mock-extended

060 GitHub stars

ユースケース

01Implementing clean architecture with explicit dependency injection in TypeScript

02Refactoring bloated class-based services into manageable pure functions

03Improving unit test isolation and reducing boilerplate in test suites

What are Skills?·How to Install

Install with 🐟 Skill.Fish

npx skillfish add jagreehal/jagreehal-claude-skills fn-args-deps

For use in Claude.ai and ChatGPT

Download Skill