How to collect return value of onbeforeunload

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I'm not certain; But I would of thought you cannot call another function, as a preventative measure by the browser so it doesn't get trapped from leaving the page.

I think only the browser knows if it's returns true / false to determine if the page is unloaded (or not).

Previously unbeforeunload was non-standard (from IE4, but supported by other browsers) Here are the Mozilla docs https://developer.mozilla.org/en/DOM/window.onbeforeunload And Microsoft docs: http://msdn.microsoft.com/en-us/library/ms536907(VS.85).aspx

However it looks as thought BeforeUnloadEvent is in the HTML5 proposal. This document gives in detail the steps that happen when a document is unloaded (interesting read):

http://www.w3.org/TR/html5/history.html#beforeunloadevent

As a workaround: You may be able to gather the information you need from the "unload event", if the unload event is NOT called after the onbeforeunload, you could assume that the user chose to stay on your page.

https://developer.mozilla.org/en/DOM/window.onunload

16,867

Ajinkya

So called human, developer, reader, StackOverflower... #1XEngineer :D @LinkedIn

Updated on July 21, 2022

Comments

Ajinkya almost 2 years

I am displaying a warning message if user try to close window without saving the form.

window.onbeforeunload = askConfirm;

    function askConfirm()
    {
        // needToConfirm is set to true if any changes are there in the form
        if (needToConfirm)
        {
            return "Your unsaved data will be lost.";
        }       
    } 

    function call_this_if_user_clicks_on_cancel()
    {
       // Bla bla bla
       // After this user should remain on the same page.
    }

Now I want to call another function when user clicks on Okay. And rest of the functionality should remain same. So how can I collect onbeforeunload return value and call another function ?

SOLUTION:

    needToConfirm = false; 
    window.onbeforeunload = askConfirm;
    window.onunload = unloadPage;
    isDelete = true;

    function unloadPage()
    {
        if(isDelete)
        {
           call_this_if_user_clicks_on_cancel() 
        }   
    }

    function askConfirm()
    {
        alert("onbeforeunload");
        if (needToConfirm)
        {
            // Message to be displayed in Warning.
            return "Your data will be lost.";
        } 
        else
        {
            isDelete = false;
        }   
    }

Ajinkya almost 13 years

@Alex: Thanks man.This is what exactly I wanted. Now it don't sound impossible.
Alex KeySmith almost 13 years

@Ajinkya: No worries glad to be of assistance, I'd be interested to see how you get along. Drop a comment on here if you get a sec if this works out ok for you.
Ajinkya almost 13 years

@Alex:Its working but onunload is called whenever I click on any other link.
Alex KeySmith almost 13 years

@Ajinkya: yeah, onbeforeunload and onunload will both be called on anything that causes the document to unload i.e. navigate somewhere else. If you need it on only certain links, you could perhaps attach the event within the click event (e.g. so attaching it just before you unload).
Ajinkya almost 13 years

@Alex: I tried some ad hoc solution.I have updates my question with solution.