Correct way to write loops for promise.

Question

How to correctly construct a loop to make sure the following promise call and the chained logger.log(res) runs synchronously through iterat

Answer 1

Bergi's suggested function is really nice:

var promiseWhile = Promise.method(function(condition, action) {
      if (!condition()) return;
    return action().then(promiseWhile.bind(null, condition, action));
});

Still I want to make a tiny addition, which makes sense, when using promises:

var promiseWhile = Promise.method(function(condition, action, lastValue) {
  if (!condition()) return lastValue;
  return action().then(promiseWhile.bind(null, condition, action));
});

This way the while loop can be embedded into a promise chain and resolves with lastValue (also if the action() is never run). See example:

var count = 10;
util.promiseWhile(
  function condition() {
    return count > 0;
  },
  function action() {
    return new Promise(function(resolve, reject) {
      count = count - 1;
      resolve(count)
    })
  },
  count)