Using a get valHook in a jQuery plugin

gistfile1.js

(function ($) {
    // jQuery plugin definition
    $.fn.bytesInput = function () {
        $(this).filter('input[type="text"]').each(function() {
            $(this).data('bytesInput', true);
        });
        return this;
    };
 
    var origHook;
 
    // There might already be valhooks for the "text" type
    if ($.valHooks.text)
        // Preserve the original valhook function
        origHook = $.valHooks.text.get;
    else
        // Make room for a new valhook
        $.valHooks.text = {};
 
    $.valHooks.text.get = function (el) {
        // Does this element have our data field?
        if (!$(el).data('bytesInput'))
            // No -- check if there was a valhook function already defined
            if (origHook)
                // There was, so go ahead and call it
                return origHook(el);
            else
                // No previous function, return undefined to have jQuery
                // take care of retrieving the value
                return undefined;
 
        // Try parsing the expression
        if (matches = el.value.match(/(\d+)\s*([kKmMgG]?)[bB]?/)) {
            switch (matches[2].toLowerCase()) {
                case 'k':
                    // Kilobytes
                    return matches[1] * 1024;
                case 'm':
                    // Megabytes
                    return matches[1] * 1048576;
                case 'g':
                    // Gigabytes
                    return matches[1] * 1073741824;
                default:
                    // Just bytes
                    return matches[1];
            }
        }
        else
            // Can't parse the expression -- just return the current value
            return el.value;
    };
})(jQuery);