$(document).ready(function() {
    var self_now_f = 0;
    var self_speed_f = 20000;
    var self_auto_change_f = null;
    var self_max_f = 0;

    var obj_f = $('.focus');

    self_max_f = $('.focus li').length;

    $('.focus li').each(function(i) {
        $(this).mouseover(function() {
        self_now_f = i;
        clearInterval(self_auto_change_f); //取消指定的setInterval函数将要执行的代码
            self_change_f(i);
        }).mouseout(function() {
        self_auto_change_f = self_interval_f();
        });
    });

    $('dl:eq(0)', obj_f).show();
    $('.focus li:eq(0)').addClass('no');

    self_auto_change_f = self_interval_f();

    function self_interval_f() {
        return setInterval(function() {//间隔指定的毫秒数不停地执行指定的代码
        self_now_f++;
            if (self_now_f >= self_max_f) {
                self_now_f = 0;
            }
            self_change_f(self_now_f);
        }, self_speed_f);
    }
    function self_change_f(i) {
        $('dl', obj_f).hide();
        $('.focus li').removeClass('no');
        $('dl:eq(' + i + ')', obj_f).show();
        $('.focus li:eq(' + i + ')').addClass('no');
    }
});