title: Get the $index of selected option in Angular
body: <p>For example: </p>
  
  <pre><code>&lt;select ng-model="selectedCategory" ng-options="category as category.title for category in categories"&gt;&lt;/select&gt;
  </code></pre>
  
  <p>Obviously, this will not work:</p>
  
  <pre><code>&lt;button ng-click="removeCategory($index)"&gt;remove&lt;/button&gt;
  </code></pre>
  
  <p>How could $index be accessed if not in a repeater?</p>