title: How to apply css using ng-class in angularjs
body: <p>I have a tag in which I want to apply class when I have no data in my field.</p>
  
  <pre><code>&lt;label class="col-xs-6 btn btn-white" ng-click="checkMultiSelect(vm.settingsObj.customfields_student,val.key)" ng-class="{'active': vm.settings.customfields_student.indexOf(????) == -1 }"&gt;
  </code></pre>
  
  <p>My settings object is like this:</p>
  
  <pre><code>"details": {
      "__v": 0,
      "_id": "58413d990533de0d1a3a4986",
      "customfields_student": [
        ""
      ],
    }
  }
  </code></pre>
  
  <p>Can any one suggest help for me on how I can apply class when it is empty?</p>