multiple files loading...

gistfile1.js

// extend Asset.js
Asset.javascripts = function(sources, options) {
    // multiple js load
    options = $merge({
        onComplete: $empty,
        onProgress: function() {}
    }, options);
    var sources = $splat(sources), counter = 0, todo = sources.length;
    sources.each(function(source) {
        Asset.javascript(source, {
            onload: function() {
                counter++;
                options.onProgress.call(this, counter, source);

                if (counter == todo)
                    options.onComplete.call(this, counter);
            }
        });
    });
};

new Asset.javascripts([
    "/js/admin/source/Swiff.Uploader.js",
    "/js/admin/source/Fx.ProgressBar.js",
    "/js/admin/source/FancyUpload2.js",
    "/js/admin/source/prodEdit.js"
], {
    onComplete: function() {
        // all done.
    },
    onProgress: function() {
        // loaded some file.
    }
});