Effect-TS

Overview

Effect is a TypeScript library that makes errors, dependencies, and async operations explicit in the type system. Instead of try-catch with unknown errors, every function declares exactly what can go wrong. Instead of global imports, every dependency is tracked in the type. The result: code that's easier to test, refactor, and reason about.

When to Use

• Business logic where knowing every possible error matters (payments, auth, data pipelines)
• Applications with complex dependency graphs that need testability
• Concurrent operations that need structured concurrency (not just Promise.all)
• Data validation and transformation pipelines
• Replacing error-prone try-catch chains with typed error handling

Instructions

Core Concept: Effect<Success, Error, Requirements>

Every Effect value has three type parameters: