title: add watch on a non scope variable in angularjs
body: <p>Is there a way to add watch to a non scope variable. I want to add a watch to local variable. I have something like this</p>
  
  <pre><code> function EditAssetRegistryController(assetregistryService, manufacturerService, assettypeService, projectService, $localStorage, $routeParams) {
          var vm = this;
          vm.manufacturers = [];
          vm.projects = [];
          vm.asset_types = [];
          vm.ch_group_uniq = 'none';
  }
  </code></pre>
  
  <p>here is there a way to add watch to vm.ch_group_uniq?
  I know how it will be done with scope variable but I have scenarios where I have to check many complex variables.</p>