FB.Connect.showPermissionDialog("offline_access");

var channel_path = 'xd_receiver.htm';
 FB_RequireFeatures(["Api"], function(){
 // Create an ApiClient object, passing app's API key and
 // a site relative URL to xd_receiver.htm
 FB.Facebook.init(api_key, channel_path);
 var api = FB.Facebook.apiClient;

 // require user to login
 api.requireLogin(function(exception){
...