$() 括号里什么都没有，是指哪个对象？

            handler.bind('mousedown', { e: me }, function(s) {
                var target = $(s.data.e);
                var oldCss = {};
                if (target.css('position') != 'absolute') {
                    try {
                        target.position(oldCss);
                    } catch (ex) { }
                    target.css('position', 'absolute');
                }
                oldCss.cursor = target.css('cursor') || 'default';
                oldCss.opacity = target.getCss('opacity') || 1;
                var dragData = {
                    left: oldCss.left || target.getCss('left') || 0,
                    top: oldCss.top || target.getCss('top') || 0,
                    width: target.width() || target.getCss('width'),
                    height: target.height() || target.getCss('height'),
                    offLeft: s.pageX,
                    offTop: s.pageY,
                    oldCss: oldCss,
                    onMove: ps.onMove,
                    onDrop: ps.onDrop,
                    handler: handler,
                    target: target
                }
                target.css('opacity', ps.opacity);
                $().bind('mousemove', { dragData: dragData }, dragndrop.drag)
                    .bind('mouseup', { dragData: dragData }, dragndrop.drop);
            });请问这个$().bind的$()是指哪个对象？我换成this,handler，程序都不行。