Redux.js vs Relay: What are the differences?

<Redux.js vs. Relay>

1. **State Management Approach**: Redux.js is primarily a state management library for JavaScript apps, providing a predictable state container that can be used with any UI layer. On the other hand, Relay is a framework developed by Facebook for building data-driven React applications. It is specifically designed to work with GraphQL, offering a declarative data fetching and updating mechanism within the components.
2. **Data Fetching**: In Redux.js, data fetching logic is typically managed within the components or thunks/sagas, where APIs are called directly. In Relay, data fetching is handled declaratively through GraphQL queries defined within the components. Relay manages data-fetching on the client based on the components' data dependencies specified in the queries.
3. **Component Ownership**: In Redux.js, the components are in control of fetching data, handling actions, and updating the store. In Relay, the framework takes ownership of data fetching and updating, allowing components to focus on rendering and specifying their data requirements through GraphQL.
4. **Server Communication**: Redux.js does not impose any specific requirements for server communication. Developers can choose any backend API solution. In contrast, Relay is tightly coupled with GraphQL and requires a GraphQL server to handle the data fetching and updating operations efficiently.
5. **Local State Management**: Redux.js is commonly used for managing both local and global state in applications, enabling developers to have a unified approach to handling state. However, Relay focuses primarily on managing remote data through the GraphQL layer and does not provide direct support for local state management within components.
6. **Community Support**: Redux.js has a large and active community with a wide range of extensions, middleware, and resources available to developers. On the other hand, Relay has a more limited community base, primarily due to its specific focus on GraphQL integration and the learning curve associated with its unique data-fetching mechanism.

In Summary, Redux.js and Relay differ in their approaches to state management, data fetching, component ownership, server communication, local state management, and community support.