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

app.controller('NavCtrl', function($scope, $location) {
  $scope.isActive = function(route) {
    $scope.path = $location.path();
    return $location.path() === route;
  };
});
<!DOCTYPE html>
<html>

  <head>
    <meta charset="utf-8" />
    <title>AngularJS Plunker</title>
    <script>document.write('<base href="' + document.location + '" />');</script>
    <link href="style.css" rel="stylesheet" />
    <script data-semver="1.2.7" src="http://code.angularjs.org/1.2.7/angular.js" data-require="angular.js@1.2.x"></script>
    <script src="app.js"></script>
  </head>

  <body ng-app="plunker" ng-controller="NavCtrl">
    <p>Click one of the following choices.</p>
    <ul>
      <li ng-class="{active: isActive('/tab1')}"><a href="#/tab1">tab 1</a></li>
      <li ng-class="{active: isActive('/tab2')}"><a href="#/tab2">tab 2</a></li>
    </ul>
    <pre>{{ path }}</pre>
  </body>

</html>
/* Put your css in here */

.active {
  background: gray;
  color: white;
}