Conditional onbeforeunload event in a page

Question

window.onbeforeunload = function(evt) {
    var message = 'Are you sure you want to leave the page. All data will be lost!';

    if (typeof evt === 'undefined') {
        evt = window.event;
    }
    if (evt && !($("#a_exit").click)) {
        evt.returnValue = message;
    }
    return message;
};

I want user to leave the page clicking to the link (has id ="a_exit") only. In other circumstances such as refreshing the page, clicking another link, user will be prompted that if he/she wants to leave the page. I have tried to use the code above. It still asks me if I want to go away when I click the exit link.

Answer 1

You can return null when you do not want the prompt to show. Tested on Chrome 79.

window.onbeforeunload = () =>  {
    if(shouldPrompt){
       return true
    }else{
       return null
    }
}

BTW modern browser no longer support custom onBeforeUnload promp text.

Answer 2

My quick example of the conditional prompt before leaving page:

    window.onbeforeunload = confirmExit;
    function confirmExit(event) {
        var messageText = tinymce.get('mMessageBody').getContent();
        messageText = messageText.trim();

        // ... whatever you want

        if (messageText != "")
            return true;
        else
            return void (0);
   };

It works under Chrome, FF.