用了alert(); 会弹出两次，而且后面的输出内容也是输出两次
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>认识语句</title>
<script type="text/javascript">
alert("此次不过是某一时刻的内心活动");
alert("但是为什么会弹出两次");
document.write("I");
document.write("love");
document.write(" you");
</script>
</head>
<body>
</body>
</html>
