获取AngularJS中最后一列的不同合计

<div ng-app="myApp" ng-controller="myCtrl">
  <table>
    <thead>
      <tr>
        <th>列1</th>
        <th>列2</th>
        <th>列3</th>
        <th>合计</th>
      </tr>
    </thead>
    <tbody>
      <tr ng-repeat="data in dataArray">
        <td>{{data.column1}}</td>
        <td>{{data.column2}}</td>
        <td>{{data.column3}}</td>
        <td>{{data.column1 + data.column2 + data.column3}}</td>
      </tr>
    </tbody>
    <tfoot>
      <tr>
        <td colspan="3">总计</td>
        <td>{{total}}</td>
      </tr>
    </tfoot>
  </table>
</div>

angular.module('myApp', [])
  .controller('myCtrl', function($scope) {
    $scope.dataArray = [
      {column1: 1, column2: 2, column3: 3},
      {column1: 4, column2: 5, column3: 6},
      {column1: 7, column2: 8, column3: 9}
    ];
    
    $scope.total = 0;
    angular.forEach($scope.dataArray, function(data) {
      $scope.total += data.column1 + data.column2 + data.column3;
    });
  });