与onbeforeunload一起出现问题并进行确认

Question

I've written some code that's supposed to fire a confirm dialog box when a user leaves the page. If the user provides confirmation, a popup window is supposed to appear; otherwise, it shouldn't. However, the onbeforeunload bit isn't firing—I don't understand why. As it's probably apparent, I'm kind of a JavaScript newbie.

window.onbeforeunload = function () {
    if (confirm("Would you like to take a short survey?")) {
        w = 1000;
        h = 1000;
        var left = (screen.width/2)-(w/2);
        var top = (screen.height/2)-(h/2);
        window.open('http://www.google.com','toolbar=0,resizable = 1, scrollbars = 1, width='+w+',height='+h+', top ='+top+', left='+left);
    }
}

Answer 1

Since 25 May 2011, the HTML5 specification states that calls to window.alert(), window.confirm(), and window.prompt() methods may be ignored during this event. See the HTML5 specification for more details.

Source: developer.mozilla.org

The function should return the text to be displayed in the confirm dialog:

window.onbeforeunload = function(e) {
    return 'You are leaving this page.';
};

but it will not necessarily work in all browsers.