简单的计时
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>滴答编程(dida100.com)</title>
</head>
<body>
<p>点击按钮，在等待 3 秒后弹出 "Hello"。</p>
<button onclick="myFunction()">点我</button>
<script>
function myFunction(){
setTimeout(function(){alert("Hello")},3000);
}
</script>
</body>
</html>