Javascript addEventListener 不适用于 onbeforeunload
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/10919790/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
addEventListener not working with onbeforeunload
提问by zconnelly13
window.addEventListener("onbeforeunload",function() {return "are you sure?"});
^ This does not seem to work... at all... the page will simply close without displaying the confirmation box...
^ 这似乎不起作用......根本......页面将简单地关闭而不显示确认框......
I realize that...
我意识到...
window.onbeforeunload = function() {return "are you sure?"}
Will work, but I want to add to the functionality (e.g. add many event listeners to the "onbeforeunload" function) not rewrite the function completely!
将工作，但我想添加到功能（例如，将许多事件侦听器添加到“onbeforeunload”函数）而不是完全重写该函数！
回答by meder omuraliev
Remove the onfrom onbeforeunload.
取出on从onbeforeunload。
Also, be aware that addEventListenerwill not work in the older IE's and possibly other browsers. If you want consistent event binding use a library.
另外，请注意，这addEventListener在较旧的 IE 和可能的其他浏览器中不起作用。如果您想要一致的事件绑定，请使用库。
回答by user7610
There is an "almost cross-browser working example" at Mozila Developer Network API reference for beforeunload event. Use their code.
在 Mozila Developer Network API 参考中有一个“几乎跨浏览器的工作示例”，用于 beforeunload 事件。使用他们的代码。
in 2014, that was
在 2014 年，那是
window.addEventListener("beforeunload", function (e) {
var confirmationMessage = "\o/";
(e || window.event).returnValue = confirmationMessage; //Gecko + IE
return confirmationMessage; //Webkit, Safari, Chrome etc.
});
in 2020, it now is
在 2020 年，现在是
window.addEventListener('beforeunload', (event) => {
// Cancel the event as stated by the standard.
event.preventDefault();
// Chrome requires returnValue to be set.
event.returnValue = '';
});
all of the above?
上述所有的？
If I ever needed this, I'd want to entrust the job to a library. If I had to do this myself, I imagine one can do all of the above, just to be extra sure
如果我需要这个，我想把这项工作委托给图书馆。如果我必须自己做这件事，我想我可以做到以上所有，只是为了更加确定
- do not try to set meaningful message text, it will only give inconsistent UX
event = event || window.eventevent.preventDefault(), maybe after check that preventDefault is defined?event.returnValue = ''return ''
- 不要尝试设置有意义的消息文本，它只会给出不一致的用户体验
event = event || window.eventevent.preventDefault()，也许在检查了 preventDefault 的定义之后？event.returnValue = ''return ''
回答by Tayeaba Mila
There's no prefix onfor the EventListenersbut it's applicable or may I say necessary for EventHandlers
EventListeners没有前缀on，但它是适用的，或者我可以说EventHandlers 是必要的
So, just keep in mind that
所以，请记住
EventHandlers = prefix on
EventListeners = prefix off
EventHandlers =前缀
EventListeners =前缀关闭
