page2.html

<!DOCTYPE html>
<html>
  <head>
    <title></title>
    <meta charset="utf-8" />
    <script>
      // Allow window to listen for a postMessage
      window.addEventListener("message", event => {
        // Normally you would check event.origin
        // To verify the targetOrigin matches
        // this window's domain
        const txt = document.querySelector("#txtMsg");
        // event.data contains the message sent
        txt.value = event.data.phoneNumber
          ? `Phone Number is ${event.data.phoneNumber}`
          : "Not Clicked";
      });

      function closeMe() {
        try {
          window.close();
        } catch (e) {
          console.log(e);
        }

        try {
          self.close();
        } catch (e) {
          console.log(e);
        }
      }
    </script>
  </head>

  <body>
    <form>
      <h1>Recipient of postMessage</h1>
      <fieldset>
        <input type="text" id="txtMsg" style="width:300px" />
        <input
          type="button"
          id="btnCloseMe"
          value="Close me"
          onclick="closeMe();"
        />
      </fieldset>
    </form>
  </body>
</html>