updateStateV6.js

const setStatus = (status, message) => SET_STATUS({ status, message });
const getResponseJson = async response => response.json();
const fetchUrl = url => () => fetch(url);

function updateState(dispatch) {
  const dispatchStatus = status => () => dispatch(setStatus(status));
  const dispatchError = ({ message }) => dispatch(setStatus('error', message));
  const dispatchState = data => dispatch(SET_STATE({ data }));

  return Promise.resolve()
    .then(dispatchStatus('submitting'))
    .then(fetchUrl('https://example.com/api/a'))
    .then(dispatchStatus('processing'))
    .then(fetchUrl('https://example.com/api/b'))
    .then(getResponseJson)
    .then(dispatchState)
    .catch(dispatchError)
    .finally(dispatchStatus('finished'));
}