AngularJS Example:

HTML

<link rel="stylesheet" href="http://twitter.github.com/bootstrap/assets/css/bootstrap.css">
<div ng-app>
  <div ng-controller="testCtrl">
       <select ng-model="lang" >
<option value="dutch">Dutch</option>
<option value="english">English</option>
</select>
    </div>
</div>

CSS

.clicked 
{
background-color:red;
}

JavaScript

function testCtrl($scope) {
        $scope.$watch("lang",function (newValue, oldValue ) {
       console.log( "lang", newValue );
    });

  }