<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
<title>test-onfocus</title>
<script type="text/javascript">
function message(){
alert("请在此输入姓名！");
}
</script>
</head>
<body>
<form>
姓名<input type="text" name="username" value="请输入姓名！" onfocus="message()">
</form>
</body>
</html>为什么不会出现你们说的无限次弹框的问题啊