How do you properly return multiple values from a Promise?

You can't resolve a promise with multiple properties just like you can't return multiple values from a function. A promise conceptually represents a value over time so while you can represent composite values you can't put multiple values in a promise.

A promise inherently resolves with a single value - this is part of how Q works, how the Promises/A+ spec works and how the abstraction works.

The closest you can get is use Q.spread and return arrays or use ES6 destructuring if it's supported or you're willing to use a transpilation tool like BabelJS.

As for passing context down a promise chain please refer to Bergi's excellent canonical on that.

you can only pass one value, but it can be an array with multiples values within, as example:

function step1(){  let server = "myserver.com";  let data = "so much data, very impresive";  return Promise.resolve([server, data]);}

on the other side, you can use the destructuring expression for ES2015 to get the individual values.

function step2([server, data]){  console.log(server); // print "myserver.com"  console.log(data);   // print "so much data, very impresive"  return Promise.resolve("done");}

to call both promise, chaining them:

step1().then(step2).then((msg)=>{  console.log(msg); // print "done"})

You can return an object containing both values — there's nothing wrong with that.

Another strategy is to keep the value, via closures, instead of passing it through:

somethingAsync().then(afterSomething);function afterSomething(amazingData) {  return processAsync(amazingData).then(function (processedData) {    // both amazingData and processedData are in scope here  });}

Fully rather than partially inlined form (equivalent, arguably more consistent):

somethingAsync().then(function (amazingData) {  return processAsync(amazingData).then(function (processedData) {    // both amazingData and processedData are in scope here  });}