jQuery: Extending bind() to define context of execution (scope)

function() {
    jQuery.extend(jQuery.event, {
        add: function(elem, types, handler, data, scope) {
            if ( elem.nodeType == 3 || elem.nodeType == 8 )
                return;

            // For whatever reason, IE has trouble passing the window object
            // around, causing it to be cloned in the process
            if ( elem.setInterval && elem != window )
                elem = window;

            // Make sure that the function being executed has a unique ID
            if ( !handler.guid )
                handler.guid = this.guid++;

            // if data or scope is defined, use a proxy function
            if( data !== undefined || scope !== undefined) {
                // Create temporary function pointer to original handler
                var fn = handler;

                // Create unique handler function, wrapped around original handler
                if ( scope !== undefined) {
                    // Create proxy function to apply correct context determined by scope
                    var proxyFn = function(){ return fn.apply(scope, arguments); };
                    handler = this.proxy( fn, proxyFn );
                } else {
                    handler = this.proxy( fn );
                }
            }

            // if data is passed, bind to handler
            if ( data !== undefined ) {
                // Store data in unique handler
                handler.data = data;
            }

            // Init the element's event structure
            var events = jQuery.data(elem, "events") || jQuery.data(elem, "events", {}),
                handle = jQuery.data(elem, "handle") || jQuery.data(elem, "handle", function(){
                    // Handle the second event of a trigger and when
                    // an event is called after a page has unloaded
                    return typeof jQuery !== "undefined" && !jQuery.event.triggered ?
                        jQuery.event.handle.apply(arguments.callee.elem, arguments) :
                        undefined;
                });
            // Add elem as a property of the handle function
            // This is to prevent a memory leak with non-native
            // event in IE.
            handle.elem = elem;

            // Handle multiple events separated by a space
            // jQuery(...).bind("mouseover mouseout", fn);
            jQuery.each(types.split(/\s+/), function(index, type) {
                // Namespaced event handlers
                var namespaces = type.split(".");
                type = namespaces.shift();
                handler.type = namespaces.slice().sort().join(".");

                // Get the current list of functions bound to this event
                var handlers = events[type];

                if ( jQuery.event.specialAll[type] )
                    jQuery.event.specialAll[type].setup.call(elem, data, namespaces);

                // Init the event handler queue
                if (!handlers) {
                    handlers = events[type] = {};

                    // Check for a special event handler
                    // Only use addEventListener/attachEvent if the special
                    // events handler returns false
                    if ( !jQuery.event.special[type] || jQuery.event.special[type].setup.call(elem, data, namespaces) === false ) {
                        // Bind the global event handler to the element
                        if (elem.addEventListener)
                            elem.addEventListener(type, handle, false);
                        else if (elem.attachEvent)
                            elem.attachEvent("on" + type, handle);
                    }
                }

                // Add the function to the element's handler list
                handlers[handler.guid] = handler;

                // Keep track of which events have been used, for global triggering
                jQuery.event.global[type] = true;
            });

            // Nullify elem to prevent memory leaks in IE
            elem = null;
        }
    });

    jQuery.fn.extend({
        bind: function( type, data, fn, scope ) {
            return type == "unload" ? this.one(type, data, fn, fn && scope) : this.each(function(){
                jQuery.event.add( this, type, fn || data, fn && data, (fn && data) && scope );
            });
        }
    });
}();