onunload和onbeforeunload无法正常工作

Question

I have this script in my aspx page

<script language="JavaScript" type="text/javascript">     
    window.onbeforeunload = function(e) {
        return 'Bye now!';
    }; 
</script>

But this is not invoked when I close the browser. I need to pop an alert asking the user to confirm. I need to do this in the aspx page using javascript. The browser I tried was mozilla firefox. Thanks

Answer 1

The following code should fix your issue:

(function () {
    window.unloader = function(e) {
       (e || window.event).returnValue = null;
       return null;
    };
    window.addEventListener("beforeunload", window.unloader);
})();

You are not going to be able to specify a message, it is defaulted by the browser.