window.attachEvent doesn't seem to be working in IE8

Question

Top page:

...
<script>
if (window.addEventListener) {
 // addEventListener equivalent of code below
} else if (window.attachEvent) {
 window.attachEvent("message", function(e) {
  if (e.origin != "page2.html") { return; }
  alert(e.data);
 });
}
</script>

<iframe src="page2.html"></iframe>

page2.html:

<script>
var message = "hello!";
parent.postMessage(message, '*');
</script>

This code works fine in Chrome, Firefox and Opera. Of course IE has its own way of doing things so this code doesn't work despite using its own .attachEvent.

The page2.html is actually a page on another domain; I'm sending the correct P3P headers (shouldn't matter, but there's that).

How do I find out why postMessage doesn't seem to be reaching the parent page?

Answer 1

attachEvent takes its event name in the form "onmessage", as opposed to addEventListener (which uses "message")