| <!DOCTYPE html> | |
| <script> | |
| const channel = new MessageChannel(); | |
| window.parent.postMessage(channel.port2, '*', [channel.port2]); | |
| channel.port1.onmessage = e => { channel.port1.postMessage("message event received") }; | |
| channel.port1.onmessageerror = () => channel.port1.postMessage("messageerror event received"); | |
| </script> |