A simple function that resolves when a call eventually does not fail or rejects after a timeout - nice for tests performing async work

eventually.js

export default function eventually(callback, timeout = 2000, pollInterval = 50) {
  return new Promise((resolve, reject) => {
    let intervalTimer;
    let lastError;

    const timeoutTimer = setTimeout(() => {
      if (!intervalTimer) return;

      clearTimeout(intervalTimer);
      reject(lastError || new Error('eventually timed out'));
    }, timeout);

    async function check() {
      try {
        const result = await callback();
        clearTimeout(timeoutTimer);
        resolve(result);
      } catch (e) {
        lastError = e;
        intervalTimer = setTimeout(check, pollInterval);
      }
    }

    check();
  });
}

// You can use this in your tests to actively wait for changes:
//
// it('succeeds eventually', async () => {
//   component.doSomething();
//   
//   await eventually(() => {
//     expect(component.hasSomeDesiredState()).toBe(true);
//   });
// });