javascript - 怎样才能使代码中的onunload事件的alert输出来？改了几次都出不来。但是打断点是能跳入事件中的。
<!DOCTYPE html>
<html>
<head>
<title>04-UI事件</title>
<meta charset="utf-8">
<style type="text/css">
p{
padding: 50px;
}
#d0{background-color: gray; margin: 20px auto;}
#d1{background-color: green;}
#d2{background-color: skyblue;}
</style>
<script type="text/javascript">
window.onunload = function () {
alert('unload');
};
window.onresize = function () {
console.log('resized');
};
window.onscroll = function () {
console.log('scroll');
};
</script>
</head>
<body>
<p id="d0">
<p id="d1">
<input type="button" value="点击一下">
<a href="http://www.baidu.com">百度一下</a>
<input type="button" value="再点击一下">
</p>
</p>
</body>
</html>
