What are Branded Types in TypeScript?

Branded types allow you to create distinct types for the same primitive, such as distinguishing between Cents and Dollars, which prevents the compiler from letting you mix them accidentally.

Why use Result types instead of standard try/catch blocks?

Result types make potential errors explicit in the function signature, forcing the caller to handle failures and reducing the risk of unhandled exceptions crashing the application.

Can I use this with existing TypeScript projects?

Yes, the skill includes a migration strategy for adopting functional patterns incrementally, starting with new features or high-risk areas like financial calculations.

How does this skill improve code reliability?

It moves logic checks from runtime to the type system, using exhaustiveness checking to ensure that every possible state of a union type is explicitly handled by the developer.

TypeScript Functional Patterns

Name: TypeScript Functional Patterns
Author: martinffx

bymartinffx

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API Development

Implements reliable TypeScript systems using algebraic data types, type-safe error handling, and branded nominal typing.

This skill empowers Claude with specialized knowledge to apply advanced functional programming patterns to TypeScript projects. It focuses on creating robust domain models where illegal states are unrepresentable by leveraging discriminated unions, exhaustiveness checking, and custom Option/Result types. By shifting error detection from runtime to compile-time, this skill helps developers build highly maintainable, self-documenting codebases that are resilient to refactoring and logic errors in complex enterprise environments.

Key Features

01Nominal typing via Branded Types for unit and ID safety

023 GitHub stars

03Type-safe error handling with Result and Option types

04Domain-driven design patterns for state machine modeling

05Automated exhaustiveness checking using assertNever patterns

06Algebraic Data Types (ADTs) and Discriminated Unions

Use Cases

01Modeling complex business logic and multi-step state transitions

02Enforcing domain invariants like validated email formats or currency units

03Eliminating runtime null or undefined errors in API responses

What are Skills?·How to Install

Install with 🐟 Skill.Fish

npx skillfish add martinffx/claude-code-atelier functional-patterns

For use in Claude.ai and ChatGPT

Download Skill