functype
Scala-Inspired Functional Programming for TypeScript
Type-safe, immutable, and composable data structures with unified interfaces
import { Option, Either } from "functype"
// Handle null safety with Option
const user = Option(maybeUser)
.map(u => u.name)
.getOrElse("Guest")
// Elegant error handling with Either
const result = Either
.fromTry(() => JSON.parse(data))
.map(obj => obj.value)Why Functype?
A functional programming library designed for TypeScript developers who value type safety and composition
Scala-Style API
Familiar constructor functions with method chaining. Works like Scala's collections API.
High Performance
Do-notation is 12x faster for List comprehensions compared to traditional flatMap chains.
Unified Interfaces
All types implement the same hierarchy of interfaces. Learn once, use everywhere.
Tree-Shakeable
Import only what you need. Optimized for minimal bundle size with selective imports.
Explore the Complete Feature Matrix
See at a glance which functional programming interfaces are supported by each data structure
View Feature Matrix →Core Data Structures
Explore the foundational types that power functional programming in TypeScript
Option<T>
Safe handling of nullable values with Some and None
Either<L,R>
Express success/failure with Left and Right values
List<A>
Immutable arrays with functional operations
Task<T>
Async operations with cancellation and error handling
Do-Notation
Scala-like for-comprehensions for monadic composition
Match & Cond
Powerful pattern matching and conditional expressions
Quick Start
Get up and running with functype in minutes
Install functype
npm install functypeAlso works with yarn, pnpm, and bun
Import what you need
import { Option, Either, List } from "functype"
// Or use selective imports for smaller bundles
import { Option } from "functype/option"Start coding functionally
const result = Option(user)
.map(u => u.email)
.filter(email => email.includes("@"))
.getOrElse("no-email@example.com")Ready to learn more?
Claude Code Skills
AI-powered development tools to accelerate your functype workflow. Install these skills in Claude Code for intelligent code assistance, pattern conversion, and library contribution guidance.
Functype User
For Application Developers
Transform imperative TypeScript code to functional patterns with AI guidance. Get instant pattern suggestions, API lookups, and debugging help while working with Option, Either, List, and more.
Functype Developer
For Library Contributors
Comprehensive guide for contributing to functype. Learn the architecture patterns, create new data structures, implement functional interfaces, and follow library conventions.
Quick Installation
Install functype skills in Claude Code using the marketplace:
Learn more about skills at github.com/jordanburke/functype