Generator functions post data and to watch for location change

WatcherGeneratorStrategy.js

function* main() {
  // create variable for watcher
  const watcherInstance = yield fork(watcher);

  // if location changes, continuation
  yield take(LOCATION_CHANGE);
  yield cancel(watcherInstance); // cancel task instance
}

function* watcher() {
  try {
    while (true) {
      const action = yield take(POST_CONFIGURATION);
      yield call(sendConfiguration, action);
    }
  } finally {
    if (yield cancelled()) {
      console.log('watcher cancelled');
    }
  }
}

function sendConfiguration(action) {
  const { payload: { values, resolve, reject } } = action;

  const url = `${apiHost}/some/api/endpoint`;
  const data = values.toJS();

  fetch(url, {
    method: 'POST',
    headers: {
      Accept: 'application/json',
      'Content-Type': 'application/json',
    },
    body: JSON.stringify(data),
  })
  .then(response => {
    if (response.ok) {
      resolve(response);
    } else { // Network 404 error
      reject(new SubmissionError({ _error: 'Network error.' }));
    }
  })
  .catch(error => {
    reject(new SubmissionError({ _error: `Server error: ${error}` }));
  });
}

export default [
  main,
];