如何确定JavaScript中window.onbeforeunload中的哪个控件导致了该事件

Question

I have set up in javascript:

var    onBeforeUnloadFired = false;

window.onbeforeunload = function (sender, args)

{
   if(window.event){
      if(!onBeforeUnloadFired) {
         onBeforeUnloadFired = true;
         window.event.returnValue = 'You will lose any unsaved changes!'; //IE
      }
   }
   else {
      return 'You will lose any unsaved changes!'; //FX
   }

   windows.setTimeout("ResetOnBeforeUnloadFired()", 1000);
}

function ResetOnBeforeUnloadFired() {
   //Need this variable to prevent IE firing twice.
   onBeforeUnloadFired = false;
}

I'm trying to achieve an edit screen where the user is warned before navigating away. It works fine except I get the pop up for normal post backs of button clicks. I'm hoping to avoid this so I'm figuring if I could determine which button was pressed it would work.

Does anybody know how to determine which button was pressed in the windows.onbeforeunload?

Alternatively anyone know a better approach to what I'm trying to achieve?

Answer 1

Another method, if you can't "control" that deep you controls, is to mark somewhat the "good controls", that is the ones which should not trigger the away-navigation logic. That is easily achievable setting a global javascript variable such as

var isGoodLink=false;
window.onbeforeunload = function (e) {
  var message = "Whatever";
  e = e || window.event;
  if (!isGoodLink) {
  // For IE and Firefox
  if (e) {
    e.returnValue = message;
  }
  // For Safari
  return message;
  }
};
function setGoodLink() {
  isGoodLink=true;
}

And add the setGoodLink function on the events you want to keep safe:

<button type="button" onclick="javascript:setGoodLink() ">I am a good button!</button>

Answer 2

Solved this by putting into an update panel all edit items TextBoxes etc.

Now the windows.onbeforeunload only fires for components external to this.