window.onbeforeunload not showing messages in chrome

Question

I'm showing an alert message on certain conditions when an user tries to leave. The message is shown in Safari, but it doesn't work in Chrome.
I tried two things like following:

window.onbeforeunload = function(event) {
    if ($scope.isFormChanged == true) {
        event.returnValue = 'Don\'t go yet! Save your changed data before you leave!';
    }
}

    window.onbeforeunload = function() {
        if ($scope.isFormChanged == true) {
            return 'Don\'t go yet! Save your changed data before you leave!'
        }
    }

Answer 1

I think this works in chrome. And I have also doubt with isFormChanged.

<script type="text/javascript"> window.onbeforeunload = function() { return "Are you sure you want to close window?" } </script>