Hey everyone!

I’ve been working on a lightweight React hook that I called useAsync that mimics some of the essential features of React Query (like fetching, caching, retries, etc.) but in a more compact, easily customizable package. Below is a quick breakdown of how it works internally, referencing the relevant code sections. If you want to see the entire code, head over to the repo:

Full Source Code on GitHub.
The hook is also available on npm as api-refetch.

Why Making My Own Hook?

While React Query and SWR are both great libraries, I wanted a more hands-on approach for a few reasons:

1. Lightweight Footprint
   
   While React Query and SWR are feature-rich, they can be relatively large (React Query ~2.2 MB, SWR ~620 kB). api-refetch is around 250 kB, making it ideal for smaller apps where bundle size is a big concern. This hook as meant to be installed as a dependency of another library (Intlayer). As a result, the size of the solution was an important consideration.

2. Easy to Customize & Optimize
   I needed some specific capabilities—like storing/fetching data from local storage and managing parallel requests using a straightforward approach.
   By cloning the repo or copying the code directly into your project, you can strip out any unwanted features and keep only what you need. This not only reduces bundle size but also minimizes unnecessary re-renders and increase, giving you a leaner, more performant solution tailored to your specific requirements.

3. No Required Provider
   
   I wanted to avoid Context Provider to make the hook global, and keep it's usage as simple as possible. So I made a version of the hooke based on a Zustand store (see example bellow).

4. Learning Exercise
   
   Building an async library from scratch is an excellent way to understand concurrency, caching, and state management internals.

In short, rolling my own hook was a chance to hone in on precisely the features I need (and skip the ones I don’t) while keeping the library small and easy to understand.

Covered Features

The React hook manage:

• Fetching & State Management: Handles loading, error, success, and fetched states.
• Caching & Storage: Optionally caches data (via React states or Zustand under the hood) and offers local storage support.
• Retries & Revalidation: Configurable retry limits and automatic revalidation intervals.
• Activation & Invalidation: Automatically activates and invalidates queries depending on other queries' or states. Example: automatically fetch some data when the user logs in. And invalidate it when the user logs out.
• Parallel Component Mount Fetching: Prevents multiple simultaneous requests for the same resource when multiple components mount at once.

How the Code Works

Below are the key points in api-refetch and short references to the relevant parts of the code in useAsync.tsx.

1. Fetching and Handling Parallel Mounting

• Code Snippet:

  // This map stores any in-progress Promise to avoid sending parallel requests
  // for the same resource across multiple components.
  const pendingPromises = new Map();

  const fetch: T = async (...args) => {
    // Check if a request with the same key + args is already running
    if (pendingPromises.has(keyWithArgs)) {
      return pendingPromises.get(keyWithArgs);
    }

    // Otherwise, store a new Promise and execute
    const promise = (async () => {
      setQueryState(keyWithArgs, { isLoading: true });

      // ...perform fetch here...
    })();

    // Keep it in the map until it resolves or rejects
    pendingPromises.set(keyWithArgs, promise);
    return await promise;
  };

• Explanation: Here, we store any ongoing fetch in a pendingPromises map. When two components try to fetch the same resource simultaneously (by having the same keyWithArgs), the second one just reuses the ongoing request instead of making a duplicate network call.

2. Revalidation

• Code Snippet:

  // Handle periodic revalidation if caching is enabled
  useEffect(
    () => {
      if (!revalidationEnabled || revalidateTime <= 0) return; // Revalidation is disabled
      if (!isEnabled || !enabled) return; // Hook is disabled
      if (isLoading) return; // Fetch is already in progress
      if (!isSuccess || !fetchedDateTime) return; // Should retry either of revalidate
      if (!(cacheEnabled || storeEnabled)) return; // Useless to revalidate if caching is disabled

      const timeout = setTimeout(() => {
        fetch(...storedArgsRef.current);
      }, revalidateTime);

      return () => clearTimeout(timeout);
    },
    [
      /* dependencies */
    ]
  );

• Explanation: Whenever you enable revalidation, api-refetch checks if the cached data is older than a specified revalidateTime. If it is, the data is automatically re-fetched in the background to keep your UI in sync without extra manual triggers.

3. Retry Logic

• Code Snippet:

  useEffect(
    () => {
      const isRetryEnabled = errorCount > 0 && retryLimit > 0;
      const isRetryLimitReached = errorCount > retryLimit;

      if (!isEnabled || !enabled) return; // Hook is disabled
      if (!isRetryEnabled) return; // Retry is disabled
      if (isRetryLimitReached) return; // Retry limit has been reached
      if (!(cacheEnabled || storeEnabled)) return; // Useless to retry if caching is disabled
      if (isLoading) return; // Fetch is already in progress
      if (isSuccess) return; // Hook has already fetched successfully

      const timeout = setTimeout(() => {
        fetch(...storedArgsRef.current);
      }, retryTime);

      return () => clearTimeout(timeout);
    },
    [
      /* dependencies */
    ]
  );

• Explanation: On error, the hook counts how many failed attempts have occurred. If it’s still below the retryLimit, it automatically waits retryTime milliseconds before trying again. This process continues until data is successfully fetched or the retry limit is reached.

4. Auto-Fetch

• Code Snippet:

  // Auto-fetch data on hook mount if autoFetch is true
  useEffect(
    () => {
      if (!autoFetch) return; // Auto-fetch is disabled
      if (!isEnabled || !enabled) return; // Hook is disabled
      if (isFetched && !isInvalidated) return; // Hook have already fetched or invalidated
      if (isLoading) return; // Fetch is already in progress

      fetch(...storedArgsRef.current);
    },
    [
      /* dependencies */
    ]
  );

• Explanation: With autoFetch set to true, the hook will automatically run the async function as soon as the component mounts—perfect for “fire-and-forget” scenarios where you always want the data on load.

See the Full Source on GitHub

Check out the complete code, which includes local storage logic, query invalidation, and more here:

• Full Source Code

Feel free to give it a try, report issues, or contribute if you’re interested. Any feedback is much appreciated!

Example of use

Installation

Copy the code or code the (repo)[https://github.com/aymericzip/api-refetch]

Or

  // This map stores any in-progress Promise to avoid sending parallel requests
  // for the same resource across multiple components.
  const pendingPromises = new Map();

  const fetch: T = async (...args) => {
    // Check if a request with the same key + args is already running
    if (pendingPromises.has(keyWithArgs)) {
      return pendingPromises.get(keyWithArgs);
    }

    // Otherwise, store a new Promise and execute
    const promise = (async () => {
      setQueryState(keyWithArgs, { isLoading: true });

      // ...perform fetch here...
    })();

    // Keep it in the map until it resolves or rejects
    pendingPromises.set(keyWithArgs, promise);
    return await promise;
  };

Quick Example

  // Handle periodic revalidation if caching is enabled
  useEffect(
    () => {
      if (!revalidationEnabled || revalidateTime <= 0) return; // Revalidation is disabled
      if (!isEnabled || !enabled) return; // Hook is disabled
      if (isLoading) return; // Fetch is already in progress
      if (!isSuccess || !fetchedDateTime) return; // Should retry either of revalidate
      if (!(cacheEnabled || storeEnabled)) return; // Useless to revalidate if caching is disabled

      const timeout = setTimeout(() => {
        fetch(...storedArgsRef.current);
      }, revalidateTime);

      return () => clearTimeout(timeout);
    },
    [
      /* dependencies */
    ]
  );

That’s it! Give it a try, and let me know how it goes. Feedback, questions, or contributions are more than welcome on GitHub.

GitHub: api-refetch

Happy coding!

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