AngularJS and Bootstrap Progress Bar

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

app.controller('MainCtrl', function($scope) {
  $scope.progress = 0;
  
  var reversing = false;
  window.setInterval(function() {
    $scope.$apply(function() {
      if (reversing) {
        $scope.progress -= 1;
      } else {
        $scope.progress += 1;
      }
      
      if ($scope.progress >= 100) {
        reversing = true;
      } else if ($scope.progress <= 0) {
        reversing = false;
      }
    });
  }, 100)
})
.directive('progressBar', function() {
  return {
    restrict: 'A',
    link: function(scope, element, attrs) {
      var watchFor = attrs.progressBarWatch;
      
      // update now
      var val = scope[watchFor];
      element.attr('aria-valuenow', val)
        .css('width', val+"%");
      
      // watch for the value
      scope.$watch(watchFor, function(val) {
        element.attr('aria-valuenow', val)
          .css('width', val+"%");
      })
    }
  }
})

<!DOCTYPE html>
<html ng-app="plunker">

  <head>
    <meta charset="utf-8" />
    <title>AngularJS Plunker</title>
    <script>document.write('<base href="' + document.location + '" />');</script>
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta name="description" content="" />
    <meta name="author" content="" />
    <!-- Le styles -->
    <link data-require="bootstrap-css" data-semver="3.0.0" rel="stylesheet" href="//netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap.min.css" />
    <link data-require="bootstrap@*" data-semver="3.0.0" rel="stylesheet" href="//netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap.min.css" />
    <style>
      body {
        padding-top: 60px;
      }
      @media (max-width: 979px) {

        /* Remove any padding from the body */
        body {
          padding-top: 0;
        }
      }
    </style>
    <link href="style.css" rel="stylesheet" />
    <!-- Le HTML5 shim, for IE6-8 support of HTML5 elements -->
    <!--[if lt IE 9]>
      <script src="//html5shim.googlecode.com/svn/trunk/html5.js"></script>
    <![endif]-->
    <!-- Le fav and touch icons -->
    <link rel="shortcut icon" href="images/favicon.ico" />
    <link rel="apple-touch-icon" href="images/apple-touch-icon.png" />
    <link rel="apple-touch-icon" sizes="72x72" href="images/apple-touch-icon-72x72.png" />
    <link rel="apple-touch-icon" sizes="114x114" href="images/apple-touch-icon-114x114.png" />
    <!-- Le javascript
    ================================================== -->
    <script data-require="jquery" data-semver="2.0.3" src="http://code.jquery.com/jquery-2.0.3.min.js"></script>
    <script data-require="bootstrap" data-semver="3.0.0" src="//netdna.bootstrapcdn.com/bootstrap/3.0.0/js/bootstrap.min.js"></script>
    <script data-require="angular.js@1.0.x" src="https://ajax.googleapis.com/ajax/libs/angularjs/1.0.8/angular.min.js" data-semver="1.0.8"></script>
    <script src="app.js"></script>
  </head>

  <body ng-controller="MainCtrl">
    <div class="progress">
      <div class="progress-bar" role="progressbar" progress-bar-watch="progress" progress-bar aria-valuenow="" aria-valuemin="0" aria-valuemax="100" style=""></div>
    </div>
  </body>

</html>

/* Put your css in here */