setTimeout(x, 0) not delaying in Chrome

Question

I have a web page with a form on it; I want to warn the user if they move away. I haven't implemented dirty checking so my onbeforeunload code is simply

window.onbeforeunload = function () {
    return 'message'
};

I don't want this warning when they submit the form, so I remove the event on submit. However, the submit may fail , so I need to put the event back afterwards (so if they then navigate away they still get warned). To that end I have done the following:

var tempDisableBeforeUnload = function() {
    var obu = window.onbeforeunload;
    if (obu) {
        window.onbeforeunload = null;
        setTimeout(function() {
            window.onbeforeunload = obu;
        }, 0);
    }
}
$("form.noWarnOnSubmit").submit(tempDisableBeforeUnload);

This works fine in Firefox and IE - the setTimeout(x, 0) defers the restoration of the event handler until after the submit has decided whether it is successful or not .

However, in Chrome, the timeout appears to occur immediately, and I get the warning when I submit my form.

How can I make this work on Chrome, or how else can I achieve the end of "don't warn on submit, but put the warning back if the submit fails"?

Answer 1

Cant you do the following:

var unloadActive = true;
window.onbeforeunload = function () {
    if(unloadActive) return 'message'
};
$("form.noWarnOnSubmit").submit(function(event){
    unloadActive = false;
    // do all your checks and things, whatever, and if the checks fail:
    unloadActive = true;
});

Then you don't need to do all that function juggling which might cause issues. I haven't tested this, but this is how I would do it.

Answer 2

I have overcome my immediate issue by

• Binding my event to fire after the jQuery validation event, by deferring my submit event binding:

$(function() {
    $("form.noWarnOnSubmit").submit(disableBeforeUnloadIfNotCancelled);
});

• Changing my event handler to only unbind the onbeforeunload event if the submit event is cancelled.

var disableBeforeUnloadIfNotCancelled = function (e) {
    if (!e.isDefaultPrevented()) {
        window.onbeforeunload = null;
    }
}