效果如下：
<script type="text/javascript">
??? function colok() {
?????? var now = new Date();?????? //获取日期对象
?????? var year = now.getYear();?? //获取年
?????? var month = now.getMonth(); //获取月份
?????? var date = now.getDate();?? //获取日
?????? var day = now.getDay();???? //获取星期
?????? var hour = now.getHours();? //获取小时
?????? var minu = now.getMinutes();//获取分
?????? var sec = now.getSeconds(); //获取秒
?????? var week;
?????? month = month + 1;
?????? if (month < 10){
?????????? month = "0" + month; //当月份小于10时，前补零
?????? }
?????? if (date < 10){
?????????? date = "0" + date;?????? //当日期小于10时，前补零
?????? }
?????? if (hour < 10){
?????????? hour = "0" + hour;?????? //当小时小于10时，前补零
?????? }
?????? if (minu < 10){
?????????? minu = "0" + minu;?????? //当分钟小于10时，前补零
?????? }
?????? if (sec < 10){
?????? ??? sec = "0" + sec;???? //当秒小于10时，前补零
?????? }
?????? var arr_week = new Array("星期日", "星期一", "星期二", "星期三", "星期四", "星期五",
????????????? "星期六");
?????? week = arr_week[day];
?????? var time = "";
?????? time = year + "年" + month + "月" + date + "日 " + week + " " + hour + ":"
????????????? + minu + ":" + sec;//拼接显示的字符串
?????? document.getElementById("time").innerHTML = "[" + time + "]";
?????? var timer = setTimeout("colok()", 1000);//每隔1000毫秒自动执行函数
??? }
</script>
??? </head>
??? <body onLoad="colok()">
?????? <div id="time"></div>
</body>