How to Prevent Unnecessary State Updates from Async Thunks in a React/Redux App

Learn how to effectively manage async calls in your React and Redux apps to avoid unwanted state updates when users navigate away from a page.
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This video is based on the question https://stackoverflow.com/q/66900441/ asked by the user 'cbdeveloper' ( https://stackoverflow.com/u/10128619/ ) and on the answer https://stackoverflow.com/a/66901380/ provided by the user 'Linda Paiste' ( https://stackoverflow.com/u/10431574/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Managing Async Calls in a React/Redux App

Navigating between different pages in a single-page application (SPA) built with React and Redux is a common scenario. However, if not managed correctly, it can lead to unexpected behaviors, especially when dealing with asynchronous calls. A common problem developers face is how to handle pending async actions that complete after the user has navigated to another page.

The Problem: Stale Async Calls Updating State

Imagine a scenario where a user navigates to a guide page:

The user visits blog/slug-1, and a loadPageThunk() is dispatched.

The guide data starts to fetch, which may take several seconds to complete.

While waiting, the user navigates away from this page to blog/slug-2.

Meanwhile, the async operation fetching blog/slug-1 completes and tries to update the state.

This results in the application showing the content of the old post (blog/slug-1) on the new page (blog/slug-2), leading to a confusing experience for users.

The Solution: A Structured Approach

Understanding State Management

The key to preventing such unwanted state updates is to implement a well-defined state management strategy that keeps track of which async operation is currently active. Here are steps you can take:

Use Unique Identifiers: Assign a unique ID for each LOAD_PAGE operation. This ID can represent a cycle or session, essentially acting like a version number for the content fetching process.

Store Data as Entities: Organize your data into entities. For example:

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This structure allows every page to save its own data and retrieve it later, irrespective of the current page.

Implementation Steps

Here’s how you can implement this strategy in your app:

Dispatch Load Action with ID: When you dispatch your loadPageThunk(), include a unique ID. This could simply be a timestamp or a counter.

Check ID in Reducer: In your reducer, before updating the state with the fetched data, check if the ID matches the current page’s ID. Only then should you allow the update:

[[See Video to Reveal this Text or Code Snippet]]

Cleanup on Navigation: Use useEffect to reset the state when unmounting a component, ensuring stale data does not linger. Dispatch a RESET action to clear any previous data:

[[See Video to Reveal this Text or Code Snippet]]

Benefits of This Approach

Consistency: The UI reflects the correct data based on current navigation, thus enhancing user experience.

Scalability: As your application grows, managing data with entities and collections makes it easier to maintain.

Separation of Concerns: Each page component remains responsible for its own data without worrying about other components’ states.

Conclusion

Managing async calls effectively in a React/Redux application is crucial in providing a smooth user experience. By implementing unique identifiers for each load cycle and structuring your state management to separate entity data, you’ll prevent unwanted state updates from stale async actions. Embrace these best practices today to build robust, user-friendly applications.