Reduce boilerplate of adding functions to a function queue

Question

I'm working with animation in JavaScript, and I have a bunch of functions you can call to add things to the animation queue. Basically, all of these functions look like this:

function foo(arg1, arg2) {
    _eventQueue.push(function() {
        // actual logic
    }
 }

I'm wondering now if it would be possible to cut down on this boilerplate a little bit, though, so I don't need that extra "_eventQueue" line in each function body dozens of times. Would it be possible, for example, to make a helper function which takes an arbitrary function as an argument and returns a new function which is augmented to be automatically added to the event queue? The only problem is that I need to find a way to maintain access to the function's original arguments in this process, which is... complicated.

SLaks · Accepted Answer · 2010-04-22 19:36:55Z

3

You're looking for the arguments identifier, which gives an array-like object containing the arguments that were passed to the current function.

For example:

function createEnqueuer(func) {
    return function() {
        var outerArgs = arguments;

        _eventQueue.push(function() {
            return func.apply(window, outerArgs);
        });
    };
}

answered Apr 22, 2010 at 19:36

SLaks

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6 Comments

Joey Adams Over a year ago

Dang, beat me to it. However, I'm not sure I agree with calling apply with this set to window. Although this code currently follows existing JavaScript convention (by matching what this is set to when you call a function not as a method), it provides little benefit, and it is subject to change in EMCAScript 5. If I'm not mistaken, this will be set to undefined instead. Disclaimer: I am by no means an expert on this subject; I just so happened to watch this yesterday: yuiblog.com/blog/2010/02/24/video-crockonjs-3 .

s4y Over a year ago

Can you see any potential issues with calling func.apply(this, outerArgs)?

Derek Thurn Over a year ago

Awesome... how does this work? I would have assumed that the arguments array would hold the arguments to the createEnqueuer function, not to the func function.

SLaks Over a year ago

@thurn: The arguments keyword gives the arguments of whatever function it's referenced in. (even if the function doesn't declare any arguments)

Derek Thurn Over a year ago

@SLaks: Oh! I get it. 'arguments' refers to the arguments of the anonymous function you return, but it's invoked with all of the arguments of the original function. I was confused because I forgot you didn't have to declare all of a function's arguments in the signature... you can just pass them in and access them via the arguments array. That is some cool stuff!

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