升序：
<ul>
<li ng-repeat="user in users | orderBy:user.index">{{user.name}}</li>
</ul>
倒序：
<ul>
<li ng-repeat="user in users | orderBy:user.index:'desc'">{{user.name}}</li>
</ul>
升序：
<ul>
<li ng-repeat="user in users | orderBy:user.index">{{user.name}}</li>
</ul>
倒序：
<ul>
<li ng-repeat="user in users | orderBy:user.index:'desc'">{{user.name}}</li>
</ul>