Head-to-Head: Harlem vs Effector Analysis


v3.1.8(9 months ago)

This package is actively maintained.Types definitions are bundled with the npm packageNumber of direct dependencies: 1Monthly npm downloads

@harlem/core is a state management library for JavaScript applications. It provides a simple and intuitive API for managing application state and handling state changes. With @harlem/core, you can easily define and update reactive state variables, create computed properties, and subscribe to state changes.

Alternatives: redux, mobx, vuex

Tags: javascriptstate-managementreactivelightweight


v23.0.0(2 days ago)

This package is actively maintained.Types definitions are bundled with the npm packageNumber of direct dependencies: 0Monthly npm downloads

Effector is a JavaScript library for building predictable and fast state machines and reactive applications. It provides a composable approach to handling state, where each state change is represented by an event, and each event corresponds to a specific set of state changes. Effector has a clear separation between logic and effects, making it easy to test and debug. It also has a built-in mechanism for handling subscriptions and side-effects.

Alternatives: redux, mobx, xstate

Tags: javascriptstate-managementreactive-programmingframework-agnostic



Effector has gained a lot of popularity in recent years and has a growing community. It is widely adopted and used in production by many developers. On the other hand, @harlem/core is a newer package and has a smaller community compared to Effector.

Use Case

Effector is a full-featured state management library that emphasizes predictable state updates and allows for efficient handling of complex logic flows. It provides advanced features like stores, events, and effects, making it suitable for large-scale applications. @harlem/core, on the other hand, is a lightweight and minimalistic state management library specifically designed for React applications.

API Design

Effector has a more complex and expressive API due to its extensive feature set. It provides powerful abstractions like stores, events, and effects, but this can result in a steeper learning curve. @harlem/core, on the other hand, has a simpler and more intuitive API, focusing primarily on easy state management within React components.

Developer Experience

Effector provides excellent developer experience with strong TypeScript support, good documentation, and active community support. It has well-maintained tools and utilities to enhance the development process. @harlem/core also offers a smooth developer experience with TypeScript support and thorough documentation, although its community and tooling ecosystem are not as mature as Effector's.


Both @harlem/core and Effector are designed with performance in mind. Effector emphasizes performance optimizations through its efficient subscription model and minimized re-renders. @harlem/core also focuses on performance and provides optimized updates for React components. When it comes to performance, it is always recommended to benchmark and test the specific use case to determine the optimal solution.


Effector can be used with various frameworks and libraries beyond React, making it versatile for multi-framework projects. On the other hand, @harlem/core is specifically designed for React and integrates seamlessly with React components, allowing for intuitive state management within the React ecosystem.


Both @harlem/core and Effector are actively maintained by their respective communities. Effector has a larger community and a more established maintenance track record, while @harlem/core is relatively newer and its maintenance depends on the activity of its maintainers and contributors.