Is there any way in Backbone to get a list of all of a model's properties that have been changed since the last sync? model.changedAttributes() only works for the most recent change (and only inside of a 'change' event listener).
The reason I ask: I'm working on a system that only syncs model attributes that have changed - it doesn't send the entire JSON of every changed model. To do that it currently has to keep track of which attributes are 'dirty' or not for each model.
That said, if you need something fancier, and can't you simply listen on "change" events, and stash the last set of changed attributes where you can look them up later?