Angular:

http://angularjs.org/

by mrajcok

HTML

<div ng-controller="MyCtrl">
    <ul>
        <li ng-repeat="itemL1 in mainMenuL1Arr" ng-click="selectL2menu(itemL1.name)">{{itemL1.name}}</li>
    </ul>
    <ul style="margin-left: 20px">
        <li ng-repeat="itemL2 in mainMenuL2CurArr"><a href="#">
             <span>{{itemL2.name}}</span>
        </a>
        </li>
    </ul>
</div>

JavaScript

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

function MyCtrl($scope) {
    $scope.mainMenuL1Arr = [ {name: 'one'}, {name: 'two'} ];
    $scope.mainMenuL2Obj = { 
        one: [ {name: '1.1'}, {name: '1.2'} ],
        two: [ {name: '2.1'}, {name: '2.2'} ] };
    $scope.mainMenuL2CurArr = $scope.mainMenuL2Obj['one'];
    $scope.selectL2menu = function (itemL1name) {
        console.log(itemL1name);
        $scope.mainMenuL2CurArr = $scope.mainMenuL2Obj[itemL1name];
    };
}