generics-as-functions

Design TypeScript generics as functions between types with constraints.

Updated Jul 17, 2017

Search Tags:#typescript #documentation #constraints #generics #type-level #tsdoc #type-utils

Ready to run

npx skills add https://github.com/luyi985/lyi-bash --skill generics-as-functions

💬 Prompt for ChatGPT / Claude Chat▼

Please help me install this Agent Skill.
Skill: generics-as-functions
Source: https://github.com/luyi985/lyi-bash/tree/main/ai/skills/generics-as-functions
Command: npx skills add https://github.com/luyi985/lyi-bash --skill generics-as-functions

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve?

Generics are powerful but can become hard to reason about when used without a clear mental model. This Skill helps you treat generics as functions between types to design safer, more reusable type-level constructs in TypeScript.

Core Features & Use Cases

Define constrained generic types and functions that transform or constrain inputs.
Build reusable type utilities and document them with TSDoc for strong developer experience.
Apply the generics-as-functions approach to both simple and complex type-level patterns in real-world projects.

Quick Start

Define a constrained generic type and demonstrate its usage with an example like picking a subset of properties from a type.

Frequently Asked Questions about generics-as-functions

High-intent search queries and answers about installing and using this skill.

FAQPage Schema

How do I constrain TypeScript generics so they accept only specific types?▼

TypeScript generics are constrained using the extends keyword on type parameters, ensuring inputs meet specific structural requirements. This approach treats generics as functions that validate and transform type-level inputs before returning derived types.

What is the generics-as-functions mental model in TypeScript?▼

The generics-as-functions model treats TypeScript generics as functions mapping input types to output types. This framework clarifies complex type-level constructs like mapped types and conditional types by viewing type parameters as function arguments and return types.

How do I write TSDoc comments for generic type utilities like Partial and Pick?▼

Documenting generic type utilities with TSDoc requires annotating type parameters, constraints, and return behavior above the type declaration. This practice ensures strong developer experience when reusing utilities like Partial and Pick across type-level codebases.

How do I use keyof and mapped types to build reusable TypeScript type utilities?▼

Use keyof to extract union types from object keys and mapped types to iterate over them, creating reusable utilities. Combined with the generics-as-functions approach, this enables constructing type-level transformations like Pick and Partial safely.

When should I use conditional types in TypeScript generic functions?▼

Conditional types should be used when generic type-level logic needs to branch based on input type relationships. They allow TypeScript generics to behave like functions with conditional logic, returning different types depending on how constraints and extends clauses evaluate.

Do I need to understand conditional types before using advanced TypeScript generics?▼

Yes, understanding conditional types, keyof, and mapped types is required to design advanced TypeScript generics effectively. These features form the foundation for treating generics as functions that perform complex type-level transformations and constraints.