先上代码
<!DOCTYPE html>
<html>
<head>
<script>
function startTime()
{
var today=new Date();
var h=today.getHours();
var m=today.getMinutes();
var s=today.getSeconds();
// add a zero in front of numbers<10
m=checkTime(m);
s=checkTime(s);
document.getElementById('txt').innerHTML=h+":"+m+":"+s;
t=setTimeout(function(){startTime()},500);
} function checkTime(i)
{
if (i<10)
{
i="0" + i;
}
return i;
}
</script>
</head> <body onload="startTime()">
<div id="txt"></div>
</body>
</html>
核心方法: setTimeout
这个方法规定了以某个时间间隔执行某个事件或函数,和oc的NSTimer很像