facebook permissions : How to check if the user has already allowed publish_stream for your app

wanted to know how to check if the user has already allowed your application to publish on his stream ( to avoid the momentarily popup menu). Currently I'm simply using this javascript

 

++++++++++++++++++++++++++++++++++++++++

 

 

 
  < 
  script 
  > 
  
 
  <!-- 
  
Facebook.showPermissionDialog( 
  ' 
  publish_stream,read_stream 
  ' 
  );
 
  // 
  --> 
  
 
  < 
  / 
  script>