cross domain iframe communication

If you need to send data to and from iFrames there are numerous different methods however alot of them are outdated or just to complicated. Why not use postMessage:

//on the sending end, within iframe
var domain = document.referrer;
postMessage(window.frameElement, 'http://'+domain);

//on the receiving end, the parent page
window.addEventListener('message',function(){
 event.source.postMessage('{"somedata":"value", "ohmoredata":"value"}', event.origin);
},false);

You can send json object back and forth in order to easily send more than on piece of data with limited amount of calls to each iframe.

Also by using event.source and event.origin you do not need to hard code the domain values to each message, making the code reusage across multiple domains.