effect

effect

Effect is a library for building robust, maintainable, type-safe, and production grade applications in TypeScript.

The effect package is the core of the framework. It provides primitives for managing side effects, errors, concurrency, resources, and structured data, alongside a rich standard library.

Requirements

• TypeScript 5.9 or newer

• Strict type-checking: the strict flag must be enabled in your tsconfig.json:

  {
    "compilerOptions": {
      "strict": true
    }
  }
  

Installation

npm install effect@beta

Documentation

• Effect website
• API reference

Overview

The effect package is a collection of modules. Some of the core ones:

Module	Description
Effect	The core abstraction for managing side effects, concurrency, and error handling in a structured way.
Context	A lightweight dependency injection mechanism that enables passing services through computations without direct references.
Layer	A system for managing dependencies, allowing for modular and composable resource allocation.
Fiber	Lightweight virtual threads with resource-safe cancellation capabilities, enabling many features in Effect.
Stream	A powerful abstraction for handling asynchronous, event-driven data processing.
Schedule	A module for defining retry and repeat policies with composable schedules.
Scope	Manages the lifecycle of resources, ensuring proper acquisition and release.
Schema	A powerful library for defining, validating, and transforming structured data with type-safe encoding and decoding.

In v4, functionality that previously lived in separate packages ships inside effect under the effect/unstable/* namespaces, including http, httpapi, rpc, cluster, workflow, cli, ai, sql, and reactivity.

Similar packages

Other packages similar to effect

fp-ts

A TypeScript functional-programming library with abstractions such as Either, Option, and TaskEither. It offers composable functional building blocks, while the package described here provides a more integrated effect runtime, including services, resource management, and concurrency.

neverthrow

A lightweight library for representing success and failure with Result and ResultAsync. It is a focused choice for typed error handling; the package described here covers a broader range of runtime concerns, including dependency management and concurrent execution.

rxjs

A library for composing asynchronous and event-based programs with Observables and operators. It is especially suited to streams of events and reactive data flows, whereas the package described here centers on typed effects, services, and resource-safe program execution.

zod

A TypeScript-first schema validation library for parsing and validating runtime data. It overlaps with the package described here on schema-based validation, but is primarily focused on schemas rather than effect composition, concurrency, and resource lifecycles.