iframe_listener.html

//%python

//import base64

//html64 = base64.b64encode("""
<div id=a>adfadfas</div>
<script>
function test(msg){
  document.getElementById('a').innerHTML = msg;
}
function listener(event){
	test(event.data);
}
if (window.addEventListener){
  addEventListener("message", listener, false)
} else {
  attachEvent("onmessage", listener)
}
</script>
<input type=button name=xxxxxxxxxxxxxxx value=test onclick=test('changed')>
//""")

//displayHTML("""
<iframe name=iframe1 id=iframe1 width=2000 height=1000 src=\"data:text/html;base64,""" + html64 + """\"></iframe>
<script>
function sleep(ms) {
  return new Promise(resolve => setTimeout(resolve, ms));
}
async function sendMessage(msg){
  await sleep(300);
  document.getElementById('iframe1').contentWindow.postMessage(msg,'*');
}
sendMessage('aaaaaaaaaaaa');
</script>
//""")