javascript - how to append active color to the li element on filtering? -

i want append active class li element based on filtering in angular,i tried ng-class iam not getting.

here html code:

 <div class="input-group dropdown" style="margin-top:50px;margin-  left:100px;">    <input type="text"  class="form-control" ng-model="input.val" data-toggle="dropdown" aria-describedby="basic-addon2" ng-change="fnautocompletequestion(input.val)"  >        <div class="dropdown-menu width-menu">            <ul style="width: 225px; height: auto; overflow: auto; list-style-type: none;margin-left: -30px;">                <li ng-repeat="value in data | filter: input.val" ng-class="{'active': $index == value.txt}  ng-click="input.val=value.txt">                         {{value.txt}}                   <hr ng-show="!$last" style="margin-top: -1px; margin-bottom: 12px;">                </li>             </ul>         </div> 

css

  .active{         color:red;     } 

any appreciated.

i think missing ''

  ng-class="{'active': $index == input.val}