Reduce Promises.js

exports.reducePromises = (fns = []) =>
  fns.reduce(
    (promise, fn) =>
      promise.then(result => {
        return fn(result)
          .then(Array.prototype.concat.bind(result))
          .catch(Array.prototype.concat.bind(result));
      }),
    Promise.resolve([])
  );

// example
const promise1 = () => new Promise(resolve => resolve(1));
const promise2 = () => new Promise(resolve => resolve(2));
const promise3 = () => new Promise((resolve, reject) => reject(3));
const promise4 = iNeedPrevResults => {
  iNeedPrevResults.forEach(prevRes => console.log("prevRes:", prevRes));

  return new Promise(resolve => resolve(4));
};

// usage
exports
  .reducePromises([promise1, promise2, promise3, promise4])
  .then(resultCollection => {
    console.log("resultCollection", resultCollection);
  })
  .catch(err => console.log("error", err));