promiseSnippet.js

// weird method 1
function someAction() {
  return fetchData()
    .then(data => {
      return cumulativePromise([data], fetchOtherData());
    })
    .then(accumulation => {
      var fetchedData = accumulation[0];
      var fetchedOtherData = accumulation[1];
      
      return cumulativePromise(accumulation, saveNewData(fetchedData));
    })
    .then((accumulation => {
     // ..etc..etc
    });
}

function cumulativePromise(values, newPromise) {
  values = values.map((value) => {
    return new Promise((resolve, reject) => {
      return resolve(value);
    });
    
    values.push(newPromise);
    
  return Promise.all(values);
}

// method 2
function someAction() {
  // promises have to be aware of how to deal with an accumulation
  var promises = [
    fetchData,
    fetchOtherData,
    saveData
  ];
  return Promise.reduce(promises, (accumulation, promise) => {
    return promise(accumulation)
      .then((val) => {
        accumulation.push(val);
        
        return accumulation;
      })
    ;
  }, []);
}