এইচটিএমএল onmessage

<!DOCTYPE html>
<html>
<body>

<button onclick="sendMessage()">বার্তা পাঠান</button>

<p id="message"></p>

<script>
window.onmessage = function(event) {
  document.getElementById("message").innerHTML =
    event.data;
};

function sendMessage() {
  window.postMessage("হ্যালো", "*");
}
</script>

</body>
</html>