Iframe Communication - inner.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Embedded Page</title>
  </head>
  <body>
    <h2>Embedded</h2>
    <textarea cols="30" rows="10" disabled id="output">waiting</textarea>
    <input type="text" id="field" />
    <button id="send">Send</button>
    <script>
      // set up references to DOM nodes
      const output = document.getElementById("output");
      const button = document.getElementById("send");
      const field = document.getElementById("field");

      // create a variable for the parent window. We will assign it once we get the first message.
      let parent = null;

      // add an event listener to send messages when the button is clicked
      button.addEventListener("click", () => {
        // don't do anything if there is no parent reference yet
        if (parent === null) {
          return;
        }

        // otherwise get the field text, and send it to the parent
        const text = field.value;
        parent.postMessage(text);
      });

      // add an event listener to run when a message is received
      window.addEventListener("message", ({ data, source }) => {
        // if we don't have a reference to the parent window yet, set it now
        if (parent === null) {
          parent = source;
        }

        // now we can do whatever we want with the message data.
        // in this case, displaying it, and then sending it back
        // wrapped in an object
        output.textContent = JSON.stringify(data);
        const response = {
          success: true,
          request: { data },
        };
        parent.postMessage(response);
      });
    </script>
  </body>
</html>