无法删除beforeunload事件

Question

We are using following code to show default pop up on refresh, tab close events

var myEvent = window.attachEvent || window.addEventListener;
var chkevent = window.attachEvent ? 'onbeforeunload' : 'beforeunload'; /// make IE7, IE8 compitable

myEvent(chkevent, function (e) { // For >=IE7, Chrome, Firefox
  if ($('#timeExpiredtxt').hasClass('hide') && $("#submittedAnsResponseText").hasClass("hide")) {
    var confirmationMessage = 'You are attempting an assessment. Are you sure you want to leave this assessment?';
    (e || window.event).returnValue = confirmationMessage;
    return confirmationMessage;
  }
});

I want to remove and unbind this event at runtime. I tried the following code but no luck.

$(window).off("beforeunload"); 
$(window).off("onbeforeunload"); 
window.onbeforeunload = null;

$(window).unbind("beforeunload");

Answer 1

Had to change the event binding code.

function closeIt() {
    if ($('#timeExpiredtxt').hasClass('hide') && $("#submittedAnsResponseText").hasClass("hide")) {
        return "Any string value here forces a dialog box to \n" +
             "appear before closing the window.";
    }
}
window.onbeforeunload = closeIt;

and unbind used below code

window.onbeforeunload = null;