javascript - Alert on Browser Back button click or page refresh

Question

I have seen the same function is multiple sites including SO. I am also trying to achieve this. Here is the code so far.

 <script>
            var myEvent = window.attachEvent || window.addEventListener;
            var chkevent = window.attachEvent ? 'onbeforeunload' : 'beforeunload'; 

            myEvent(chkevent, function(e) { // For >=IE7, Chrome, Firefox
                var confirmationMessage = ' ';  
                (e || window.event).returnValue = confirmationMessage;
                return confirmationMessage;
            });
        </script>

The problem is above code is working fine in chrome and IE but when I tried to test in on Firefox it is not working. I checked firebug but there is no error. I updated the firefox and version are 47.0.1.

But issue not fixed.

Any advice would be helpful.

Guys if you have code better than this then it would be also helpful.

Answer 1

Use below code, I tested it in firefox and is working fine :

window.addEventListener("beforeunload", function (e) {
  var confirmationMessage = "o/";

  (e || window.event).returnValue = confirmationMessage; //Gecko + IE
  return confirmationMessage;                            //Webkit, Safari, Chrome
});