javascript - Promise.all().then() resolve?

Question

Using Node 4.x. When you have a Promise.all(promises).then() what is the proper way to resolve the data and pass it to the next .then()?

I want to do something like this:

Promise.all(promises).then(function(data){
  // Do something with the data here
}).then(function(data){
  // Do more stuff here
});

But I'm not sure how to get the data to the 2nd .then(). I can't use resolve(...) in the first .then(). I figured out I can do this:

return Promise.all(promises).then(function(data){
  // Do something with the data here
  return data;
}).then(function(data){
  // Do more stuff here
});

But that doesn't seem like the proper way to do it... What is the right approach to this?

Answer 1

But that doesn't seem like the proper way to do it..

That is indeed the proper way to do it (or at least a proper way to do it). This is a key aspect of promises, they're a pipeline, and the data can be massaged by the various handlers in the pipeline.

Example:

const promises = [
  new Promise(resolve => setTimeout(resolve, 0, 1)),
  new Promise(resolve => setTimeout(resolve, 0, 2))
];
Promise.all(promises)
  .then(data => {
    console.log("First handler", data);
    return data.map(entry => entry * 10);
  })
  .then(data => {
    console.log("Second handler", data);
  });