[javascript] Can promises have multiple arguments to onFulfilled?

I'm following the spec here and I'm not sure whether it allows onFulfilled to be called with multiple arguments. For example:

promise = new Promise(function(onFulfilled, onRejected){
    onFulfilled('arg1', 'arg2');
})

such that my code:

promise.then(function(arg1, arg2){
    // ....
});

would receive both arg1 and arg2?

I don't care about how any specific promises implementation does it, I wish to follow the w3c spec for promises closely.

Since functions in Javascript can be called with any number of arguments, and the document doesn't place any restriction on the onFulfilled() method's arguments besides the below clause, I think that you can pass multiple arguments to the onFulfilled() method as long as the promise's value is the first argument.

2.2.2.1 it must be called after promise is fulfilled, with promise’s value as its first argument.

You can use E6 destructuring:

Object destructuring:

promise = new Promise(function(onFulfilled, onRejected){
    onFulfilled({arg1: value1, arg2: value2});
})

promise.then(({arg1, arg2}) => {
    // ....
});

Array destructuring:

promise = new Promise(function(onFulfilled, onRejected){
    onFulfilled([value1, value2]);
})

promise.then(([arg1, arg2]) => {
    // ....
});

The fulfillment value of a promise parallels the return value of a function and the rejection reason of a promise parallels the thrown exception of a function. Functions cannot return multiple values so promises must not have more than 1 fulfillment value.

Great question, and great answer by Benjamin, Kris, et al - many thanks!

I'm using this in a project and have created a module based on Benjamin Gruenwald's code. It's available on npmjs:

npm i -S promise-spread

Then in your code, do

require('promise-spread');

If you're using a library such as any-promise

var Promise = require('any-promise');
require('promise-spread')(Promise);

Maybe others find this useful, too!

To quote the article below, ""then" takes two arguments, a callback for a success case, and another for the failure case. Both are optional, so you can add a callback for the success or failure case only."

I usually look to this page for any basic promise questions, let me know if I am wrong

http://www.html5rocks.com/en/tutorials/es6/promises/

De-structuring Assignment in ES6 would help here.For Ex:

let [arg1, arg2] = new Promise((resolve, reject) => {
    resolve([argument1, argument2]);
});

As far as I can tell reading the ES6 Promise specification and the standard promise specification theres no clause preventing an implementation from handling this case - however its not implemented in the following libraries:

• RSVP.promise (#L516-544)
• Q promise (#787)

I assume the reason for them omiting multi arg resolves is to make changing order more succinct (i.e. as you can only return one value in a function it would make the control flow less intuitive) Example:

new Promise(function(resolve, reject) {
   return resolve(5, 4);
})
.then(function(x,y) {
   console.log(y);
   return x; //we can only return 1 value here so the next then will only have 1 argument
})
.then(function(x,y) {
    console.log(y);
});

Here is a CoffeeScript solution.

I was looking for the same solution and found seomething very intersting from this answer: Rejecting promises with multiple arguments (like $http) in AngularJS

the answer of this guy Florian

promise = deferred.promise

promise.success = (fn) ->
  promise.then (data) ->
   fn(data.payload, data.status, {additional: 42})
  return promise

promise.error = (fn) ->
  promise.then null, (err) ->
    fn(err)
  return promise

return promise 

And to use it:

service.get().success (arg1, arg2, arg3) ->
    # => arg1 is data.payload, arg2 is data.status, arg3 is the additional object
service.get().error (err) ->
    # => err