Just in the interest of making the function in global.js more generic, it would be great if we could add this in now to save going back and changing things later on?

To keep things simple, maybe make `callback` the second argument to get passed. Then use something like `var hasCallback = typeof(callback) == 'function'` so you can do a conditional check to see if it needs to be excecuted?

Thanks for all your work on this one!