title: How to watch an array for changes in AngularJS
body: <p>I basically want the equivalent to binding to 'add' and 'remove' events in Backbone's Collections. I see basically no way of doing this in AngularJS, and the current workaround we've settled for is <code>$watch()</code>ing the array's <code>length</code> and manually diffing/recalculating the whole thing. Is this really what the cool kids do?</p>
  
  <p><em>Edit</em>: Specifically, watching the array's length means I don't easily know which element has been changed, I need to manually "diff".</p>