Angular: NG-Class

http://angularjs.org/

HTML

<script src="http://code.angularjs.org/angular-1.0.1.js"></script>
<ul class="navigation" ng:controller="NavigationController">
        <li>Active: {{states.activeItem}}, Change here: <input ng-model="states.activeItem" /></li>
      <li ng-repeat="item in items" 
            class="item" 
            ng-class="{'color': red}" ng-click="states.activeItem=item.id">{{item.title}}</li>
    </ul>

CSS

ul.navigation li.active {
    background-color: red;
}

JavaScript

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

app.controller('NavigationController', function($scope){
    // Have to use a wrapper object, otherwise "activeItem" won't work! Just try it!
    $scope.states = {};
    $scope.states.activeItem = 'item1';
	$scope.items = [{
	  id: 'item1', title: 'Item 1'
	}, {
	  id: 'item2', title: 'Item 2'
	}, {
	  id: 'item3', title: 'Item 3'
	}];
});