Question

I want to perform a number of actions, which will execute asynchronously (sending data to the server with a ‘finished’ callback). I then want to trigger an event when all of these tasks complete. Something like a thread join without the threads. I wrote the following helper function, which does what I want:

// A quick fake for thread joining. 
// Allow objects to add and remove themselves. Once they are all removed, call the callback with the context.
function Waiter(callback, context)
{
    this.tarriers = [];
    this.callback = callback;
    this.context = context;

    this.add = function(tarrier)
    {
        this.tarriers.push(tarrier);
    }

    this.remove = function(tarrier)
    {
        this.tarriers = _.without(this.tarriers, tarrier);

        if (this.tarriers.length == 0)
        {
            this.callback(this.context);
        }
    }

    return this;
}

But I feel a bit bad about wheel-reinventing. Is there a library that I can use that does this kind of thing (plus possibly other related things) for me.

(I know that JS isn’t mulithreaded.)

Answer 1

The jQuery Deferred/Promise methods do exactly this.

http://api.jquery.com/category/deferred-object/