title: Angularjs how to get filename extension?
body: <p>Hi I am developing angularjs application. I am doing file upload module. I am trying to validate the files. I want to upload only xlsx or xls files. I have developed directive and factory method to upload files as below.</p>
  
  <pre><code>myapp.directive('fileModel', ['fileUploadExcel', function (fileUploadExcel) {
      return {
          restrict: 'A',
          link: function (scope, element, attrs) {
              element.bind("change", function (evt) {
                  fileUploadExcel.pendingFiles[attrs.fileModel] = evt.target.files[0];
              });
          }
      };
  }]);
  </code></pre>
  
  <p>Below is my controller.</p>
  
  <pre><code> $scope.upload = function (filename) {
   fileUploadExcel.doUpload().success(function (success) {
   }).error(function (error) {
  });
  </code></pre>
  
  <p>Below is my factory code.</p>
  
  <pre><code>myapp.factory('fileUploadExcel', ['$http', '$cookieStore', 'cfg', function ($http, $cookieStore, cfg) {
      var LoginID = $cookieStore.get("LoginID");
      var baseurl = cfg.Baseurl;
      var fileuploadurl = baseurl + 'api/Customer/BulkUploadVehicle/';
  
      var service = {
          uploadUrl: fileuploadurl,
          pendingFiles: {},
          doUpload: doUpload
      };
      return service;
      function doUpload() {
          var filename;
          var files = new FormData();
          files.append('LoginID', LoginID);
          angular.forEach(this.pendingFiles, function (value, index) {
              filename = value.name;
              files.append(index, value);
          });
          var extn = filename.split(".").pop();
          if (extn == 'xlsx' || extn == 'xls') {
              return $http.post(this.uploadUrl, files, {
                  transformRequest: angular.identity,
                  headers: {
                      'Content-Type': undefined
                  }
              })
          }
          else
          {
              return false;
          } 
      }
  }]);
  </code></pre>
  
  <p>I am able to get extn successfully. When my files are of type excel my code works fine. Whenever i upload other than excel i am getting error. I have wrote return false. This is not working here. I should return something else may be. May i know what i should write in else case? Can anyone help me out here? Any help would be appreciated. Thank you. </p>