What's the redux idiom for waiting for multiple async calls?

define another action creator that would act as a composition

function doEverything() {
  return dispatch => Promise.all([
    dispatch(doSomething()),
    dispatch(doSomethingElse())
  ]);
}

just write

store.dispatch(doEverything()).then(() => {
  console.log('I did everything!');
});

make it a point to return a Promise

store.dispatch(doSomething()).then(() => {
  console.log('I did something');
});

use combinators like Promise.all() to wait for completion

Promise.all([
  store.dispatch(doSomething()),
  store.dispatch(doSomethingElse())
]).then(() => {
  console.log('I did everything!');
});

Using Redux Thunk middleware, declare some action creators

import 'babel-core/polyfill'; // so I can use Promises
import fetch from 'isomorphic-fetch'; // so I can use fetch()

function doSomething() {
  return dispatch => 
    fetch(
      '/api/something'
    ).then(
      response => response.json()
    ).then(
      json => dispatch({ type: DO_SOMETHING, json }),
      err => dispatch({ type: SOMETHING_FAILED, err })
    );
}

function doSomethingElse() {
  return dispatch => 
    fetch(
      '/api/something'
    ).then(
      response => response.json()
    ).then(
      json => dispatch({ type: DO_SOMETHING_ELSE, json }),
      err => dispatch({ type: SOMETHING_ELSE_FAILED, err })
    );
}