<!-- ⚠️ AUTO-GENERATED FILE - DO NOT EDIT MANUALLY This file is automatically generated by the publishing pipeline. Any manual edits will be overwritten when the pipeline runs. To modify this file: - Run: bun run admin pipeline - Or modify the generator service in src/services/publish/generator.ts For project information, see ABOUT.md -->

[!WARNING] This is an auto-generated file. Manual edits will be overwritten by the publishing pipeline. For project information, see ABOUT.md

The Effect Patterns Hub

A community-driven knowledge base of practical, goal-oriented patterns for building robust applications with Effect-TS.

This repository is designed to be a living document that helps developers move from core concepts to advanced architectural strategies by focusing on the "why" behind the code.

EffectTalk.dev — Browse all 300+ patterns, take guided learning tours, and run code examples in the browser. Built on this repo.

• Start the Guided Tour
• Browse Patterns
• Welcome Post

Install the CLI to search, browse, and install patterns from your terminal:

bun add -g @effect-patterns/ep-cli
ep search "error handling"

Looking for machine-readable rules for AI IDEs and coding agents? See the AI Coding Rules section below.

Table of Contents

Effect Patterns

• Getting Started
• Core Concepts
• Error Management
• Resource Management
• Concurrency
• Streams
• Scheduling
• Domain Modeling
• Schema
• Platform
• Building APIs
• Making HTTP Requests
• Building Data Pipelines
• Testing
• Observability
• Tooling & Debugging

---

Getting Started

Foundational patterns for your first steps with Effect-TS.

| Pattern | Skill Level | Summary | | :--- | :--- | :--- | | Why Effect? Comparing Effect to Promise | 🟢 Beginner | Understand what Effect gives you that Promise doesn't: type-safe errors, dependency injection, and composability. | | Hello World: Your First Effect | 🟢 Beginner | Create and run your very first Effect program using Effect.succeed and Effect.runSync. | | Transform Values with Effect.map | 🟢 Beginner | Use Effect.map to transform the success value of an Effect without changing its error or dependency types. | | Handle Your First Error with Effect.fail and catchAll | 🟢 Beginner | Learn how to create Effects that can fail and how to recover from those failures using Effect.fail and Effect.catchAll. | | Run Multiple Effects in Parallel with Effect.all | 🟢 Beginner | Use Effect.all to run multiple Effects at the same time and collect all their results. | | Retry a Failed Operation with Effect.retry | 🟢 Beginner | Use Effect.retry with a Schedule to automatically retry failed operations with customizable delays and limits. |

Core Concepts

Essential building blocks for understanding and using Effect.

| Pattern | Skill Level | Summary | | :--- | :--- | :--- | | Understand the Either Data Type | 🟢 Beginner | Use Either<E, A> to represent computations that can fail, allowing you to accumulate multiple errors instead of short-circuiting on the first one. | | Chaining Computations with flatMap | 🟢 Beginner | Use flatMap to chain together computations where each step may itself be effectful, optional, or error-prone. | | Combining Values with zip | 🟢 Beginner | Use zip to combine two computations, pairing their results together in Effect, Stream, Option, or Either. | | Comparing Data by Value with Data.struct | 🟢 Beginner | Use Data.struct to create immutable, structurally-typed objects that can be compared by value, not by reference. | | Comparing Data by Value with Structural Equality | 🟢 Beginner | Use Data.struct and Equal.equals to safely compare objects by their value instead of their reference, avoiding common JavaScript pitfalls. | | Conditional Branching with if, when, and cond | 🟢 Beginner | Use combinators like if, when, and cond to express conditional logic declaratively across Effect, Stream, Option, and Either. | | Converting from Nullable, Option, or Either | 🟢 Beginner | Use fromNullable, fromOption, and fromEither to convert nullable values, Option, or Either into Effects or Streams, enabling safe and composable interop. | | Create Pre-resolved Effects with succeed and fail | 🟢 Beginner | Use Effect.succeed(value) to create an Effect that immediately succeeds with a value, and Effect.fail(error) for an Effect that immediately fails. | | Creating from Collections | 🟢 Beginner | Use fromIterable and fromArray to create Streams or Effects from arrays, iterables, or other collections, enabling batch and streaming operations. | | Creating from Synchronous and Callback Code | 🟢 Beginner | Use sync and async to lift synchronous or callback-based computations into Effect, enabling safe and composable interop with legacy code. | | Execute Asynchronous Effects with Effect.runPromise | 🟢 Beginner | Use Effect.runPromise at the 'end of the world' to execute an asynchronous Effect and get its result as a JavaScript Promise. | | Execute Synchronous Effects with Effect.runSync | 🟢 Beginner | Use Effect.runSync at the 'end of the world' to execute a purely synchronous Effect and get its value directly. | | Filtering Results with filter | 🟢 Beginner | Use filter to keep or discard results based on a predicate, across Effect, Stream, Option, and Either. | | Lifting Errors and Absence with fail, none, and left | 🟢 Beginner | Use fail, none, and left to represent errors or absence in Effect, Option, or Either, making failures explicit and type-safe. | | Lifting Values with succeed, some, and right | 🟢 Beginner | Use succeed, some, and right to lift plain values into Effect, Option, or Either, making them composable and type-safe. | | Understand the Option Data Type | 🟢 Beginner | Use Option<A> to explicitly represent a value that may or may not exist, eliminating null and undefined errors. | | Set Up a New Effect Project | 🟢 Beginner | Initialize a new Node.js project with the necessary TypeScript configuration and Effect dependencies to start building. | | Solve Promise Problems with Effect | 🟢 Beginner | Understand how Effect solves the fundamental problems of native Promises, such as untyped errors, lack of dependency injection, and no built-in cancellation. | | Transform Effect Values with map and flatMap | 🟢 Beginner | Use Effect.map for synchronous transformations and Effect.flatMap to chain operations that return another Effect. | | Transforming Values with map | 🟢 Beginner | Use map to transform the result of an Effect, Stream, Option, or Either in a declarative, type-safe way. | | Understand that Effects are Lazy Blueprints | 🟢 Beginner | An Effect is a lazy, immutable blueprint describing a computation, which does nothing until it is explicitly executed by a runtime. | | When to Use Chunk vs Array | 🟢 Beginner | Choose Chunk for Effect pipelines, Stream results, and immutable collection operations; use Array when interfacing with existing APIs. | | Understand the Three Effect Channels (A, E, R) | 🟢 Beginner | Learn about the three generic parameters of an Effect: the success value (A), the failure error (E), and the context requirements (R). | | [Use .pipe for Composition](./content