title: Pass object key in ng-change
body: <p>Is there a way to pass an object key or value with ng-change in a multi select element where ng-options is an object?</p>
  
  <p>In below example, the <code>$scope.check</code> function doesn't receive any paramter, but would like it to get either the key or value.</p>
  
  <p><code>&lt;select ng-model="$scope.someArray" ng-change="$scope.check(key)" ng-options="key as val for (val, key) in $scope.options" multiple&gt;&lt;/select&gt;</code></p>
  
  <p>where 
  <code>$scope.options = {a: 1, b: 2}</code></p>