window.postMessage is a method for safely enabling cross-origin communication. Normally, scripts on different pages are only allowed to access each other if and only if the pages which executed them are at locations with the same protocol (usually both http), port number (80 being the default for http), and host (modulo document.domain being set…

window.postMessage

Domain A with iframe:
-----------------------
<iframe></iframe>
<script>
   window.addEventListener( "message",
      function (e) {
            if(e.origin !== 'http://www.domainB.com'){ return; } 
              alert(e.data);	
      },
      false);
</script>


Domain B, content for the iframe
-----------------------
$(window).load() {
  top.postMessage("message", '*');
});