title: ng-style and custom css properties
body: <p>Is it possible to add custom css properties aka css variables inside ng-style? </p>
  
  <p>I have tried to use this:</p>
  
  <pre><code>&lt;li ng-repeat="item in vm.items" ng-style="{'--index': $index}"&gt;{{item.name}}&lt;/li&gt;
  </code></pre>
  
  <p>but this doesn't work I got no --index in style attribute when inspect in developer tools.</p>