postMessage

//top page
<script type="text/javascript">
        if (typeof window.postMessage === undefined) {
            alert("not support");
        }

        function main(e)
        {
            alert("where are you from ?"+e.constructor);
        }
        window.addEventListener("message", main, true);    
    </script>


    <iframe src="HTMLPage1.htm" id="widget"></iframe>


    <script type="text/javascript">

        function postms() {
            document.getElementsByTagName("iframe")[0].contentWindow.postMessage("hello world", "http://localhost:9273");
        }
    </script>

iframe page:

 <script type="text/javascript">
       
        function messageHandler(e) {
            alert(e.origin + " come from");

            window.top.postMessage("send back", e.origin);
        }
        window.addEventListener("message", messageHandler, true);
    </script>