代码示例:(标识:eg_js_timing_setinterval)
<!DOCTYPE html>
<html>
<body>

<p>此页面上的脚本启动这个时钟:</p>

<p id="demo"></p>

<script>
var myVar = setInterval(myTimer, 1000);

function myTimer() {
  var d = new Date();
  document.getElementById("demo").innerHTML = d.toLocaleTimeString();
}
</script>

</body>
</html>
运行结果: