<html>
<head>
<script type="text/javascript">
function disp_alert()
{
alert("再打个招呼。这里演示了" + "\n" + "如何在消息框中添加折行。")
}
</script>
</head>
<body>
<input type="button" onclick="disp_alert()" value="显示消息框" />
</body>
</html>