HTML Code

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="utf-8">
  <title>postMessage demo</title>
</head>
<body>
  <pre id="out"></pre>
  <script>
    var out = document.getElementById("out");
    window.addEventListener("message", function (event) {
      if (event.origin !== location.origin) return;
      out.textContent =
        "Got from " + event.origin + ":\n" +
        JSON.stringify(event.data, null, 2) +
        "\n(no document.domain needed)";
    });
    window.postMessage(
      { type: "ping", text: "hello" },
      location.origin
    );
  </script>
</body>
</html>

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postMessage instead of document.domain (Try It)