$.fn.PageSwitch = function(options) {
                return this.each(function() {
                    var $me = $(this);
                    var instance = $me.data("PageSwitch")
                    if (!instance) {
                        instance = new PageSwitch($me, options);
                        $me.data("PageSwitch", instance)
                    }

                    $('div').PageSwitch('init')   这是怎样调用init方法的？？这样写不是将init作为参数传递进去了？

                    if ($.type(options) == "string") {
                        return instance[options]();
                    }
                })
            }