console 命令行工具 X clear

console

function showTime(){
  var date = new Date();
	var h = date.getHours();
	var m = date.getMinutes();
	var s = date.getSeconds();
  m=checkTime(m);
  s=checkTime(s);
	document.getElementById('test').innerHTML = h + ":" +  m + ":" + s;
  t = setTimeout(function(){showTime()},500);
}
function checkTime(i){
  if(i < 10)
    {
      i = '0' + i;
    }
  return i;
}

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8" />
  <title>Document</title>
</head>
<body onload="showTime()">
  <div id="test"></div>
</body>
</html>