卸载（或刷新）页面时触发卸载事件。您可以尝试运行以下代码来了解如何在 JavaScript 中实现 onunload 事件。
<!DOCTYPE html>
<html>
<body onunload="newFunc()">
<p>Close the page and see what happens!</p>
<p>This event may give unexpected results.</p>
<script>
function newFunc() {
alert("Thank you!");
}
</script>
</body>
</html>
