Angular: Empty Fiddle

http://angularjs.org/

HTML

<div ng-controller="MyCtrl">
    <ul>
        <li ng-repeat="item in items" ng-click="showChilds($index)">
            <span>{{item.name}}</span>
            <ul>
                <li ng-repeat="subItem in item.subItems" ng-show="item.active">
                    <span>---{{subItem.name}}</span>
                </li>
            </ul>
        </li>
    </ul>
</div>

CSS

li:hover{
    cursor: pointer;
}

JavaScript

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

function MyCtrl($scope) {    
    $scope.showChilds = function(index){
  
        $scope.items[index].active = !$scope.items[index].active;
        collapseAnother(index);
    };
    
    var collapseAnother = function(index){
        for(var i=0; i<$scope.items.length; i++){
            if(i!=index){
                $scope.items[i].active = false;
            }
        }
    };
    
    $scope.items = [
        {
            name: "Item1",
            subItems: [
                {name: "SubItem1"},
                {name: "SubItem2"}
            ]
        },
        {
            name: "Item2",
            subItems: [
                {name: "SubItem3"},
                {name: "SubItem4"},
                {name: "SubItem5"}
            ]
        },
        {
            name: "Item3",
            subItems: [
                {name: "SubItem6"}
            ]
        }
    ];
};