Cross Domain Message Passing

embedded.js

/*
  This code goes in the webpage that is embedded via iframe.
  
  Use of JQuery is assumed in this example

*/

function postMessage() {
  var msg = $('body').height();
  window.parent.postMessage(msg, '*');
}

//Event handler for window resize
$(window).resize(postMessage);

//Event handler for page load
$().ready(postMessage);

index.js

/*
  This code is loaded by the parent webpage. It listens for a message
  and sets the height of the element with id = id-of-iframe to the value in the message.
  
  This is pretty simple code. In a production environment there are many things posting messages
  so you should be careful about filtering for the specific message from your app.
*/

function msgReceiver(ev){
	
	var msg = ev.data;
	
  var elem = document.getElementById('id-of-iframe');
  if (elem) {
	  elem.style.height = (parseInt(msg)) + "px";
  }
}