Effector

Effector is a reactive state management library for TypeScript and JavaScript applications, designed to separate business logic from UI rendering through a graph-based event and store architecture. The library is framework-agnostic, with official bindings for React, Solid, and Vue, and has been adopted in production by companies including Aviasales, Sber, Avito, MTS, Semrush, Raiffeisen Bank, UNICEF, Joom Group, and Intouch Health, a subsidiary of Teladoc. The current release is version 23.4, marketed as Effector Atlas, featuring refined TypeScript type definitions and universal hooks support across framework bindings. Effector's core primitives are stores (createStore), events (createEvent), effects (createEffect) for async operations with automatic pending and error tracking, and domains (createDomain) for grouping related units into hierarchical namespaces. Unlike Proxy-based state managers, Effector uses plain JavaScript functions and values without hidden reactivity mechanisms, making the data flow fully traceable in debugger tools like Effector DevTools. The entire library weighs approximately 10 kilobytes minified and supports aggressive tree-shaking, so unused features are stripped during bundling. Effector initializes all business logic upfront during application startup rather than lazily on first render, which shifts computation cost to boot time and improves runtime responsiveness. The testing story is straightforward because stores and events are plain objects that can be inspected and triggered in unit tests without rendering any components. Server-side rendering is supported through the fork API, which creates isolated state instances per request, preventing cross-request contamination in Node.js server environments.