How do I use RSVP deferreds with WebSocket?

Question

I need to open multiple WebSocket connections concurrently and then perform actions once all the connections are opened.

I am using the defer(), all(), and then() methods of RSVP.js. However, neither the then() nor the catch() is being triggered, and I cannot figure out where I am going wrong.

Here is my code:

var numberOfThreads = 6,
    openSockets = function () {
        var // the deferred object
            d,
            // array of promises
            socketsOpened = [],
            // websocket object and index
            ws, i;

        // open a new WebSocket connection for each iteration
        for (i = 0; i < numberOfThreads; i += 1) {
            // create deferred object
            d = RSVP.defer();

            // push promise into array
            socketsOpened.push(d.promise);

            // create websocket connection to valid, working socket server
            ws = new WebSocket(url);

            // websocket events
            ws.onopen = function () {
                // when socket is open, resolve deferred
                d.resolve();
            };
        }

        // when all connections are open, do stuff
        RSVP
        .all(socketsOpened)
        .then(function () {
            console.log('All sockets are opened!');
        }).catch(function () {
            console.log('Oops! Something has gone wrong!');
        });
    };

openSockets();

What am I doing wrong?

Answer 1

Instead of assigning the deferred to d, I should create an array (d = []), assign each deferred to the i position of the array (d[i] = RSVP.defer()), and push d[i] into the socketsOpened array.

Here's the new code:

var numberOfThreads = 6,
    openSockets = function () {
        var // an array for deferred objects
            d = [],
            // array of promises
            socketsOpened = [],
            // websocket object and index
            ws, i;

        // open a new WebSocket connection for each iteration
        for (i = 0; i < numberOfThreads; i += 1) {
            // protect i with closure
            (function (i) {
                // create deferred object
                d[i] = RSVP.defer();

                // push promise into array
                socketsOpened.push(d[i].promise);

                // create websocket connection to valid, working socket server
                ws = new WebSocket(url);

                // websocket events
                ws.onopen = function () {
                    // when socket is open, resolve deferred
                    d[i].resolve();
                };
            }(i));
        }

        // when all connections are open, do stuff
        RSVP
        .all(socketsOpened)
        .then(function () {
            console.log('All sockets are opened!');
        }).catch(function () {
            console.log('Oops! Something has gone wrong!');
        });
    };

openSockets();

Apologies for wasting everyone's time!