Trying to detect browser close event

Have you tried this code?

window.onbeforeunload = function (event) {
    var message = 'Important: Please click on \'Save\' button to leave this page.';
    if (typeof event == 'undefined') {
        event = window.event;
    }
    if (event) {
        event.returnValue = message;
    }
    return message;
};

$(function () {
    $("a").not('#lnkLogOut').click(function () {
        window.onbeforeunload = null;
    });
    $(".btn").click(function () {
        window.onbeforeunload = null;
});
});

The second function is optional to avoid prompting while clicking on #lnkLogOut and .btn elements.

One more thing, The custom Prompt will not work in Firefox (even in latest version also). For more details about it, please go to this thread.

Referring to various articles and doing some trial and error testing, finally I developed this idea which works perfectly for me.

The idea was to detect the unload event that is triggered by closing the browser. In that case, the mouse will be out of the window, pointing out at the close button ('X').

$(window).on('mouseover', (function () {
    window.onbeforeunload = null;
}));
$(window).on('mouseout', (function () {
    window.onbeforeunload = ConfirmLeave;
}));
function ConfirmLeave() {
    return "";
}
var prevKey="";
$(document).keydown(function (e) {            
    if (e.key=="F5") {
        window.onbeforeunload = ConfirmLeave;
    }
    else if (e.key.toUpperCase() == "W" && prevKey == "CONTROL") {                
        window.onbeforeunload = ConfirmLeave;   
    }
    else if (e.key.toUpperCase() == "R" && prevKey == "CONTROL") {
        window.onbeforeunload = ConfirmLeave;
    }
    else if (e.key.toUpperCase() == "F4" && (prevKey == "ALT" || prevKey == "CONTROL")) {
        window.onbeforeunload = ConfirmLeave;
    }
    prevKey = e.key.toUpperCase();
});

The ConfirmLeave function will give the pop up default message, in case there is any need to customize the message, then return the text to be displayed instead of an empty string in function ConfirmLeave().

Try following code works for me under Linux chrome environment. Before running make sure jquery is attached to the document.

$(document).ready(function()
{
    $(window).bind("beforeunload", function() { 
        return confirm("Do you really want to close?"); 
    });
});

For simple follow following steps:

1. open http://jsfiddle.net/
2. enter something into html, css or javascript box
3. try to close tab in chrome

It should show following picture:

Hi i got a tricky solution, which works only on new browsers:

just open a websocket to your server, when the user closes the window, the onclose event will be fired