Backwards compatible window.postMessage()

XD.js

// from http://www.onlineaspect.com/2010/01/15/backwards-compatible-postmessage/

var XD = function(){
	var interval_id,
		last_hash,
		cache_bust = 1,
		attached_callback,
		window = this;
	
	return {
		postMessage: function(message, target_url, target){
			if (!target_url) return;
			target = target || parent;  // default to parent
			if (window['postMessage']){
				// the browser supports window.postMessage, so call it with a targetOrigin
				// set appropriately, based on the target_url parameter.
				target['postMessage'](message, target_url.replace(/([^:]+:\/\/[^\/]+).*/, '$1'));
			} else if (target_url){
				// the browser does not support window.postMessage, so use the window.location.hash fragment hack
				target.location = target_url.replace(/#.*$/, '') + '#' + (+new Date) + (cache_bust++) + '&' + message;
			}
		},
		receiveMessage: function(callback, source_origin){
			// browser supports window.postMessage
			if (window['postMessage']){
				// bind the callback to the actual event associated with window.postMessage
				if (callback){
					attached_callback = function(e){
						if ((typeof source_origin === 'string' && e.origin !== source_origin)
						|| (Object.prototype.toString.call(source_origin) === "[object Function]" && source_origin(e.origin) === !1)) {
							 return false;
						}
						callback(e);
					};
				}
				if (window['addEventListener']){
					window[callback ? 'addEventListener' : 'removeEventListener']('message', attached_callback, false);
				} else {
					window[callback ? 'attachEvent' : 'detachEvent']('onmessage', attached_callback);
				}
			} else {
				// a polling loop is started & callback is called whenever the location.hash changes
				interval_id && clearInterval(interval_id);
				interval_id = null;
				if (callback){
					interval_id = setInterval(function(){
						var hash = document.location.hash,
							re = /^#?\d+&/;
						if (hash !== last_hash && re.test(hash)){
							last_hash = hash;
							callback({data: hash.replace(re, '')});
						}
					}, 100);
				}
			}
		}
	};
}();