(function($) {
    $.fn.extend({
        rollList: function(option) {
            option = $.extend({
                direction: "up",
                step: 1,
                time: 23
            }, option);
            var step_coe, scroll_coe, score_coe;
            if (option.direction == "up") {
                step_coe = 1;
                scroll_coe = 1;
                score_coe = 1;
            } else {
                step_coe = -1;
                scroll_coe = -1;
                score_coe = 0;
            }
            return this.each(function() {
                var $this = $(this);
                var _this = this;
                var itemHeight;
                var temp = $("<DIV> </DIV>");
                $this.css("overflow", "hidden").children().appendTo(temp);
                $this.append(temp.clone(true)).append(temp);
                itemHeight = $this.children();
                itemHeight = itemHeight.eq(1).offset().top - itemHeight.eq(0).offset().top;
                while ($this.children(":last").offset().top - $this.offset().top <= $this.height())
                    $this.append(temp.clone(true));
                var roll;
                this.scrollTop = itemHeight * (1 - score_coe);
                roll = function() {
                    temp = setInterval(function() {
                        if (_this.scrollTop * scroll_coe >= itemHeight * score_coe) {
                            _this.scrollTop = (_this.scrollTop - itemHeight) * scroll_coe;
                        }
                        _this.scrollTop += option.step * step_coe;
                    }, option.time);
                }
                $this.hover(function() {
                    clearInterval(temp);
                }, function() {
                    roll();
                });
                roll();
            });
        }
    })
} (jQuery));