fetch with Timeout

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.