title: checkbox limitation with ng-model in angularjs
body: <p>so far I've only seen people used ng-model to bind the state of checkbox. How can I know which checkbox is checked with angularjs? for example I want to get the index of the checked checkedbox so that I can do something on the backend.</p>
  
  <p>If it were in jquery / js I can use function to catch the state of the checkbox and send the index or etc info to be send back to database.  </p>
  
  <p>my plunker : <a href="http://plnkr.co/edit/dG9cwswiVzLdjEnpSNvu?p=preview" rel="nofollow">http://plnkr.co/edit/dG9cwswiVzLdjEnpSNvu?p=preview</a></p>