window.onbeforeunload 无法在 Firefox 46 上弹出 window，所有其他浏览器都可以

Question

Firefox 46 有问题，但在所有其他浏览器上运行正常。退出页面后，我会问以下问题。 Firefox 完全忽略它。请帮忙！

window.onbeforeunload = ThisCheckExittingPage;

var ThisCheckExitWindow = 1;

// Checks before exitting
// ThisCheckExitWindow = 1;

// Does NOT check before exitting
// ThisCheckExitWindow = 0;

function ThisCheckExittingPage() {

    if (ThisCheckExitWindow == 1)
    {
        return "You are about to exit this page.";
    }
}

Answer 1

这看起来像是设计使然，因为 WindowEventHandlers.onbeforeunload - Web APIs | MDN 有这条注释：

To combat unwanted pop-ups, browsers may not display prompts created in beforeunload event handlers unless the page has been interacted with. Firefox has implemented this policy since Firefox 44 (Bugzilla).

如 relevant patch 所示，mUserHasInteracted 标志变量在 window 中发生鼠标或键盘事件后设置。

window.onbeforeunload 无法在 Firefox 46 上弹出 window，所有其他浏览器都可以

window.onbeforeunload not working on Firefox 46 in a popup window, all other browsers work

firefox

onbeforeunload