Question

I don’t have an actual use case for this, but I’m curious, whether there is a way to react (callback), if a user clicks on “stay on this page” when window.onbeforeunload was triggered.

http://jsfiddle.net/rWHU9/

function warning(){
    if(true){
      console.log('leaving');
      return "You are leaving the page";
    }
}
window.onbeforeunload = warning;​

Answer 1

There is no callback for staying on the page, but there is one for leaving the page, window.unload.

Try setting a timeout in beforeunload, then clear it in unload. If you stay, the timeout will run, otherwise it’ll be cleared.

var timeout;

function warning() {
    timeout = setTimeout(function() {
        alert('You stayed');
    }, 1000);
    return "You are leaving the page";
}

function noTimeout() {
    clearTimeout(timeout);
}

window.onbeforeunload = warning;
window.unload = noTimeout;​

DEMO: http://jsfiddle.net/aPwfz/1/