用js代码显示现在是哪年哪月哪日星期几

<script>
        function showtime() {
            var today, hour, second, minute, year, month, date;
            var strDate;
            today = new Date();
            var n_day = today.getDay();
            switch (n_day) {
                case 0:
                    {
                        strDate = "星期日"
                    } break;
                case 1:
                    {
                        strDate = "星期一"
                    } break;
                case 2:
                    {
                        strDate = "星期二"
                    } break;
                case 3:
                    {
                        strDate = "星期三"
                    } break;
                case 4:
                    {
                        strDate = "星期四"
                    } break;
                case 5:
                    {
                        strDate = "星期五"
                    } break;
                case 6:
                    {
                        strDate = "星期六"
                    } break;
                case 7:
                    {
                        strDate = "星期日"
                    } break;
            }
            year = today.getFullYear();
            month = today.getMonth() + 1;
            date = today.getDate();
            hour = today.getHours();
            minute = today.getMinutes();
            second = today.getSeconds();
            document.getElementById('time').innerHTML = year + "年" + month + "月" + date + "日" + strDate; //显示时间
            setTimeout("showtime();", 1000); //设定函数自动执行时间为 1000 ms(1 s)
        }
    </script>