Example of an asynchronous function that returns a promise which can be cancelled using the AbortController

asynchronous-fn-with-abort.ts

// The implementation below is inspired by the [example](https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal#examples)
// that shows how a fetch operation can be aborted using the signal option.
// See https://gist.github.com/tjunghans/da50cc29f3f965d587db99c2f44813f1 for an example on how `doSomethingAsync` is used.

function doSomethingAsync(
  // payload can be anything. It's just an example
  payload,
  { signal }: { signal?: AbortSignal } = {}
): Promise<any> {
  // Abort immediately if `abort` was already called.
  // The definition of `AbortException` is further down.
  if (signal?.aborted) {
    return Promise.reject(new AbortException());
  }

  // Using a promise, but it could also be a callback.
  return new Promise((resolve, reject) => {
    // Create the handler with the call to reject
    const abortHandler = () => {
      reject(new AbortException());
    };

    // setTimeout is used as an example of an async operation.
    setTimeout(() => {
      // Remove the event handler on success.
      signal?.removeEventListener("abort", abortHandler);
      resolve(payload);
    }, 1000);

    // Add the signal abort handler
    signal?.addEventListener("abort", abortHandler);
  });
}

// AbortException would normally live in its own file.
class AbortException extends DOMException {
  constructor() {
    super("Aborted", "AbortError");
  }
}