has_permission.js

var hasPermission = function(uid, cb) {
  // are we allowed to publish to the user's wall?
  var perm = "publish_stream";
  var query = FB.Data.query('select ' + perm + ' from permissions where uid={0}', uid);
  query.wait(function(rows) { cb(rows[0][perm]); });  // returns 1 or 0
}