闲着没事在闪存里看到有人需要js显示当前时间，就一时兴起写了个。
输出格式：“2013年12月18日 星期三 上午9:05:00 ”。
<script type="text/javascript"> function tick() { var hours, minutes, seconds, xfile; var intHours, intMinutes, intSeconds; var today, theday; today = new Date(); var d = [
"星期日",
"星期一",
"星期二",
"星期三",
"星期四",
"星期五",
"星期六"];
theday = today.getFullYear() + "年" + [today.getMonth() + 1] + "月" + today.getDate() + "日 " + d[today.getDay()];
intHours = today.getHours();
intMinutes = today.getMinutes();
intSeconds = today.getSeconds();
if (intHours == 0) {
hours = "12:";
xfile = " 午夜";
} else if (intHours < 12) {
hours = intHours + ":";
xfile = " 上午";
} else if (intHours == 12) {
hours = "12:";
xfile = " 正午";
} else {
intHours = intHours - 12
hours = intHours + ":";
xfile = " 下午";
}
if (intMinutes < 10) { minutes = "0" + intMinutes + ":"; } else { minutes = intMinutes + ":"; } if (intSeconds < 10) { seconds = "0" + intSeconds + " "; } else { seconds = intSeconds + " "; } timeString = theday + xfile + hours + minutes + seconds; document.getElementById("lbClock").innerHTML = timeString; window.setTimeout("tick();", 100); } window.onload = tick; </script>
PS：感谢undefined的指点，简化了很多。
以上是客户端时间，那么要想显示服务器时间怎么办呢？对于精确度要求不高的情况有个方案：
页面第一次打开时获取一次服务器时间，然后根据这个时间通过js计时器计算并显示时间。
//计算时间 function getTime() { serverTime.setSeconds(serverTime.getSeconds() + 1); myTime.innerHTML = getTimeStr(serverTime); } //输出时间格式 2014-01-01 00:01:01 function getTimeStr(t) { var result = t.getFullYear() + "-" + bl(t.getMonth() + 1) + "-" + bl(t.getDate()) + " " + bl(t.getHours()) + ":" + bl(t.getMinutes()) + ":" + bl(t.getSeconds()); return result; } //补零 function bl(n) { return n.toString().length > 1 ? n : "0" + n; } //显示时间 function showTime() { myTime = document.getElementById("lbClock"); //new Date无法转换 2014-01-01 01:01:01， - 替换成 / 之后转换正常 serverTime = new Date(myTime.innerHTML.replace(/-/g, "/")); setInterval(getTime, 1000); } var myTime = '', serverTime = ''; window.onload = showTime;