AngularJS通过ng-href动态切换网站主题样式

<!DOCTYPE html>
<html ng-app="app" ng-controller="mainCtrl">
<head >
 <meta charset="UTF-8">
 <title></title>
 //动态更新CSS样式
 <link rel="stylesheet" type="text/css" ng-href="{{theme.value}}.css">
 <script src="../angular.js"></script>
 <style type="text/css">
 h1{
  font-style:italic;
 }
 </style>
 <script type="text/javascript">
 angular.module("app", [])
  .controller("mainCtrl", function($scope){
  $scope.options = [
   {
   name:"蓝色",
   value:"blue"
   },
   {
   name:"红色",
   value:"red"
   }
  ];
  //默认选择第一个样式
  $scope.theme = $scope.options[0];
  })
 </script>
</head>
<body>
 <select ng-model="theme" ng-options="c.name for c in options">
 </select>
 <h1>Welcome</h1>
 <ul>
 <li>Home</li>
 <li>About</li>
 <li>Contact</li>
 </ul>
</body>
</html>

h1{
 color:blue;
}
ul li{
 display:inline-block;
}

h1{
 color:red;
}