Demo of listing registries

ListRegistries.gs

function listRegistries() { 
 Logger.log('Cloud IoT Core Apps Script sample'); 
 var projectId = 'your-project-id'; 
 var cloudRegion = 'us-central1'; 
 var parent = "projects/"+ projectId +"/locations/" + cloudRegion; 
 
 var response = CloudIoT.Projects.Locations.Registries.list(parent); 
 response.deviceRegistries.forEach(
   function(result) {
     console.log(result.id + '\n');
   }); 
}