Rootscope is undefined using inAppBrowser Plugin of ngCordova

1

I bind ng-click but nothing happened? I followed exactly what the doc say

    $scope.openExternal=function(){

var options = {
      location: 'yes',
      clearcache: 'yes',
      toolbar: 'no'
    };

  document.addEventListener(function () {
    $cordovaInAppBrowser.open('http://ngcordova.com', '_blank', options)
      .then(function(event) {
        // success
      })
      .catch(function(event) {
        // error
      });


    $cordovaInAppBrowser.close();

  }, false);
  }

It says rootscope is undefined, why is that?