从AngularJS 1.3开始，有一个称为$watchGroup的新方法来观察一组表达式。

$scope.foo = 'foo';
$scope.bar = 'bar';

$scope.$watchGroup(['foo','bar'],function(newValues,oldValues,scope) {
  // newValues array contains the current values of the watch expressions
  // with the indexes matching those of the watchExpression array
  // i.e.
  // newValues[0] -> $scope.foo 
  // and 
  // newValues[1] -> $scope.bar 
});