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.
Effect 4.x is a long-term support (LTS) release, with at least three years of bug and security fixes. If you are upgrading from Effect 3.x, follow the migration guide.
Installation
npm install effectRequirements
TypeScript 5.9 or newer. TypeScript 7 is recommended for the best performance and compatibility with Effect's TypeScript tooling.
Node.js 18 or newer when running Effect on Node.js.
Strict type-checking: the
strictflag must be enabled in yourtsconfig.json:{ "compilerOptions": { "strict": true } }
Links
- Website: documentation, guides, and news.
- Reference: API documentation for this package.
- Discord: ask questions, share what you're building, and talk to the core team.
- Community: meetups and events, or bring Effect to your own.
- Issues: bug reports and feature requests.
Let's talk
Whether your team is considering Effect, rolling it out, or already running it in production, we'd love to hear from you: what you're building, what works, and what you need from Effect next.
- Talk to the maintainers. Introduce your team on Discord or email contact@effectful.co. We're happy to connect privately on Slack or Discord for feedback and help with adoption.
- Production support. We're exploring how to better support teams running Effect in production. If your organization has specific support needs, let's discuss them.
- Adoption help. Our adoption partners offer implementation, consulting, team extension, training, and commercial support.
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/* namespaces, including http, http-api, rpc, cluster, workflow, cli, ai, sql, and reactivity.