Angular: Empty Fiddle

http://angularjs.org/

HTML

<div ng-controller="MyCtrl">
  <ul ng-repeat="expression in expressions | orderBy:myValueFunction">
      <li>{{expression.name}} ==== orderProp:{{expression.orderProp}} comment_id: {{expression.comment_id}}</li>
    </ul>
</div>

JavaScript

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

function MyCtrl($scope) {
    $scope.expressions = [

        {
            name: 'ex2',
            comment_id: 1,
            orderProp: 4
        },
        {
            name: 'ex3',
            comment_id: 1,
            orderProp: 3
        },
        {
            name: 'ex4',
            comment_id: 1,
            orderProp: 2
        },
           {
            name: 'ex1',
            comment_id: 0,
            orderProp: 5
        },     
        {
            name: 'ex5',
            comment_id: 1,
            orderProp: 1
        }
    ];
    
    $scope.myValueFunction = function(expression) {
        if(expression.comment_id == 0){
            return expression.comment_id;
        }else{
            return expression.orderProp;
        }
    }
    
   
}