the jQuery $.klass plugin extracted from the low-pro plugin

jquery.klass.js

/**
 * $.klass is a full port of Prototype's Class.create !
 * 
 * This code is based on the jQuery port of the Low Pro behavior framework
 * that was originally written for Prototype.
 * @see http://github.com/danwrong/low-pro-for-jquery
 */
(function($) {

    var addMethods = function(source) {
        var ancestor = this.superclass && this.superclass.prototype;
        var properties = $.keys(source);
        if ( ! $.keys({ toString: true }).length ) {
            properties.push("toString", "valueOf");
        }
        for (var i = 0, length = properties.length; i < length; i++) {
            var property = properties[i], value = source[property];
            if ( ancestor && $.isFunction(value)
                          && $.argumentNames(value)[0] == "$super" ) {
                var method = value;
                value = $.extend($.wrap((function(m) {
                    return function() {
                        return ancestor[m].apply(this, arguments)
                    };
                })(property), method), {
                    valueOf: function() { return method },
                    toString: function() { return method.toString() }
                });
            }
            this.prototype[property] = value;
        }

        return this;
    }

    $.extend({
        keys: function(obj) {
            var keys = [];
            for (var key in obj) keys.push(key);
            return keys;
        },

        argumentNames: function(func) {
            var names = func.toString().match(/^[\s\(]*function[^(]*\((.*?)\)/)[1].split(/, ?/);
            return names.length == 1 && !names[0] ? [] : names;
        },

        bind: function(func, scope) {
            return function() {
                return func.apply(scope, $.makeArray(arguments));
            }
        },

        wrap: function(func, wrapper) {
            var __method = func;
            return function() {
                return wrapper.apply(this, [$.bind(__method, this)].concat($.makeArray(arguments)));
            }
        },
        
        klass: function() {
            var parent = null, properties = $.makeArray(arguments);
            if ( $.isFunction(properties[0]) ) parent = properties.shift();

            var klass = function() { this.initialize.apply(this, arguments); };

            klass.superclass = parent;
            klass.subclasses = [];
            klass.addMethods = addMethods;

            if ( parent ) {
                var subclass = function() { };
                subclass.prototype = parent.prototype;
                klass.prototype = new subclass;
                parent.subclasses.push(klass);
            }

            for ( var i=0; i < properties.length; i++ ) {
                klass.addMethods(properties[i]);
            }

            if ( ! klass.prototype.initialize ) {
                klass.prototype.initialize = function() {};
            }

            klass.prototype.constructor = klass;
            
            return klass;
        }
    });

})(jQuery);