Javascript register window/tab closing event before window/tab close

Question

This has / may have been asked before, but, as far as I remember, the question was not satisfactory answered at that time ^^

How can I register a window or tab closi

Answer 1

window.onbeforeunload = function (e) {
  var e = e || window.event;

  // For IE and Firefox
  if (e) {
    e.returnValue = 'Any string';
  }

  // For Safari
  return 'Any string';
};