remove $$hashkey from Angular ng-repeat

angular-track-by-index.html

<ul>
    <li ng-repeat="thing in things track by $id($index)">
    .....
    </li>
</ul>


or 
<script>
  JSON.stringify(value, function (key, val) {
     if (key == '$$hashKey') {
       return undefined;
     }
     return val;
  });
</script>

angular.toJson() is enough.