JS::DeferredFnStack.js

'use strict';
const Q = require('q')

function DeferredFnStack(fn) {
  let stack = Q.when();

  return () => {
    const dfd = Q.defer();
    stack = stack.fin(() => Q.when(fn()).then(dfd.resolve, dfd.reject));
    return dfd.promise;
  };
}

/**
 * USAGE
 */

function asyncPromise(value) {
  const dfd = Q.defer();

  const resolve = () => dfd.resolve(value)
  setTimeout(resolve, 500)

  return dfd.promise
}

const fn = DeferredFnStack(function () {
  return Q.resolve('Hello World!')
    .then(asyncPromise)
    .then(asyncPromise)
});

fn().then((value) => console.log(value));
fn().then((value) => console.log(value));
fn().then((value) => console.log(value));

/*
 Outputs 3 times 'Hello World!' with 1000ms interval
 */