Sequential Promises (No Generators)

gistfile1.js

let log = (x) => {
  console.log(x);
  return x;
};

let delayedPromise = (value, delay) => {
  return new Promise((resolve) => {
    setTimeout(() => {
      resolve(value);
    }, delay);
  });
};

let promiseGenerator = (...args) => {
  return () => {
    return delayedPromise(...args).then(log);
  };
};


var promiseGenerators = [
  promiseGenerator("p1", 1000),
  promiseGenerator("p2", 1000),
  promiseGenerator("p3", 1000),
  promiseGenerator("p4", 1000)
];

var promises = promiseGenerators.reduce((promises,p) => {
  var lastPromise;
  if(promises.length === 0) {
      lastPromise = Promise.resolve();
  } else {
      lastPromise = promises[promises.length - 1];
  }
  
  let newPromise = lastPromise.then(function(results) {
      return p();
  });
  promises.push(newPromise);
  
  return promises
}, []);

var results = Promise.all(promises).then(log)