Monday, 16 January, 2023 UTC

fetch with Timeout

fetch with Timeout

Summary

A few years back I wrote a blog post about how write a fetch Promise that times out. The function was effective but the code wasn’t great, mostly because AbortController , which allows you to cancel a fetch Promise, did not yet exist. With AbortController and AbortSignal available, let’s create a better JavaScript function for fetching with a timeout:
Much like the original function, we’ll use setTimeout to time to the cancellation but we’ll use the signal with the fetch request:
async function fetchWithTimeout(url, opts = {}, timeout = 5000) {
  // Create the AbortController instance, get AbortSignal
  const abortController = new AbortController();
  const { signal } = abortController;

  // Make the fetch request
  const _fetchPromise = fetch(url, {
    ...opts,
    signal,
  });

  // Start the timer
  const timer = setTimeout(() => abortController.abort(), timeout);

  // Await the fetch with a catch in case it's aborted which signals an error
  try {
    const result = await _fetchPromise;
    clearTimeout(timer);
    return result;
  } catch (e) {
    clearTimeout(timer);
    throw e;
  }
};

// Usage
try {
  const impatientFetch = await fetchWithTimeout('/', {}, 2000);
}
catch(e) {
  console.log("fetch possibly canceled!", e);
}
The JavaScript code above is much cleaner now that we have a proper API to cancel fetch Promise calls. Attaching the signal to the fetch request allows us to use a setTimeout with abort to cancel the request after a given amount of time.
It’s been excellent seeing AbortController, AbortSignal, and fetch evolve to make async requests more controllable without drastically changing the API.
The post fetch with Timeout appeared first on David Walsh Blog.

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