WCF DataContracts include an ExtensionData property which is a bit troublesome if you are trying to send a modified object back up to the service if it has no properties in Javascript.

So I wrote a little piece of Javascript to clean it up:

function DeleteExtensionData(obj) {
	var keys = Object.keys(obj);

	keys.each(function(key) {
		if(!Object.isFunction(obj[key])) {
			if(obj[key] instanceof Object) {
				DeleteExtensionData(obj[key]);
			}

			if(key == "ExtensionData") {
				delete obj[key];
			}
		}
	});
}

It will recusively delete all ExtensionData properties from the object.  You can call as soon as you get the result from a completed AJAX request or you can call before sending an object parameter to a service.

Note that it uses constructs from prototype.

If you want to get fancy, you can also write a custom serializer.