js/libs/ember-data.js
function() {
    var oldData = get(this, '_data'),
        newData = get(this, '_attributes'),
        diffData = {},
        prop;

    for (prop in newData) {
      diffData[prop] = [oldData[prop], newData[prop]];
    }

    return diffData;
  }
function() {
    var oldData = get(this, '_data'),
        newData = get(this, '_attributes'),
        diffData = {},
        prop;

    for (prop in newData) {
      diffData[prop] = [oldData[prop], newData[prop]];
    }

    return diffData;
  }
Returns an object, whose keys are changed properties, and value is
an [oldProp, newProp] array.

Example

```javascript
App.Mascot = DS.Model.extend({
name: attr('string')
});

var person = store.createRecord('person');
person.changedAttributes(); // {}
person.set('name', 'Tomster');
person.changedAttributes(); // {name: [undefined, 'Tomster']}
```

@method changedAttributes
@return {Object} an object, whose keys are changed properties,
and value is an [oldProp, newProp] array.