Angular array sorting for object array.

var app = angular.module('plunker', []);

app.controller('MainCtrl', function($scope) {  
  
  $scope.keys = function() {
    var keys = [];
    for(key in $scope.contents[0])
    {
      if(key != '$$hashKey'){
        keys.push(key);    
      }
    }
    return keys;
  }
  
  
  $scope.contents = [
    { 
      id : '1231',
      session: '1231-1231-2392-1223',
      expires: '2013-05-26T18:35Z'
    },
    { 
      id : '3234',
      session: '1231-1231-2392-1223',
      expires: '2013-05-13T18:35Z'
    },
    { 
      id : '2432',
      session: '23234-234-23423-23423',
      expires: '2012-03-23T12:35Z'
    }
    ]
});

<!DOCTYPE html>
<html ng-app="plunker">
  
  <head>
    <meta charset="utf-8">
    <title>AngularJS Plunker</title>
    <script>
      document.write('<base href="' + document.location + '" />');
    </script>
    <link rel="stylesheet" href="style.css">
    <script data-require="angular.js@1.0.x" src="http://code.angularjs.org/1.0.7/angular.min.js" data-semver="1.0.7"></script>
    <script src="app.js"></script>
  </head>
  
  <body ng-controller="MainCtrl">
  <table class="table table-striped">
    <caption>Content</caption>
    
    <thead>
        <tr>
        <th ng-repeat="key in keys()">
        {{key}}
        </th>
        </tr>
    </thead>
    
    <tbody>
      <tr ng-repeat="content in contents | orderBy:'id':false">
        <td>
          {{content.id}}
        </td>
        <td>
          {{content.session}}
        </td>
        <td>
          {{content.expires | date}}
        </td>
      </tr>
    </tbody>
  </table>

</html>

/* Put your css in here */